23.5 stdbuf: Run a command with modified I/O stream buffering
stdbuf allows one to modify the buffering operations of the
three standard I/O streams associated with a program. Synopsis:
stdbuf option... command
command must start with the name of a program that
- uses the ISO C
FILE streams for input/output (note the
programs dd and cat don't do that),
- does not adjust the buffering of its standard streams (note the
program tee is not in this category).
Any additional args are passed as additional arguments to the
The program accepts the following options. Also see Common options.
- ‘-i mode’
- Adjust the standard input stream buffering.
- ‘-o mode’
- Adjust the standard output stream buffering.
- ‘-e mode’
- Adjust the standard error stream buffering.
The mode can be specified as follows:
- Set the stream to line buffered mode.
In this mode data is coalesced until a newline is output or
input is read from any stream attached to a terminal device.
This option is invalid with standard input.
- Disable buffering of the selected stream.
In this mode, data is output immediately and only the
amount of data requested is read from input.
Note the difference in function for input and output.
Disabling buffering for input will not influence the responsiveness
or blocking behavior of the stream input functions.
fread will still block until
EOF or error,
even if the underlying
read returns less data than requested.
- Specify the size of the buffer to use in fully buffered mode.
size may be, or may be an integer optionally followed by,
one of the following multiplicative suffixes:
‘KB’ => 1000 (KiloBytes)
‘K’ => 1024 (KibiBytes)
‘MB’ => 1000*1000 (MegaBytes)
‘M’ => 1024*1024 (MebiBytes)
‘GB’ => 1000*1000*1000 (GigaBytes)
‘G’ => 1024*1024*1024 (GibiBytes)
and so on for ‘T’, ‘P’, ‘E’, ‘Z’, and ‘Y’.
125 if stdbuf itself fails
126 if command is found but cannot be invoked
127 if command cannot be found
the exit status of command otherwise