code: func ptsname(f *os.File) (string, error) {
  	var n int32
  	if err := ioctl(f.Fd(), syscall.TIOCGPTN, uintptr(unsafe.Pointer(&n))); err != nil {
  		return "", err
  	}
  	return fmt.Sprintf("/dev/pts/%d", n), nil
  }
docs: // ptsname retrieves the name of the first available pts for the given master.