pipesz(1) — Linux manual page


PIPESZ(1)                     User Commands                    PIPESZ(1)

NAME         top

       pipesz - set or examine pipe and FIFO buffer sizes

SYNOPSIS         top

       pipesz [options] [--set size] [--] [command [argument] ...]

       pipesz [options] --get

DESCRIPTION         top

       Pipes and FIFOs maintain an internal buffer used to transfer data
       between the read end and the write end. In some cases, the
       default size of this internal buffer may not be appropriate. This
       program provides facilities to set and examine the size of these

       The --set operation sets pipe buffer sizes. If it is specified,
       it must be specified with an explicit size. Otherwise, it is
       implied and the size is read from /proc/sys/fs/pipe-max-size. The
       kernel may adjust size as described in fcntl(2). To determine the
       actual buffer sizes set, use the --verbose option. If neither
       --file nor --fd are specified, --set acts on standard output.

       The --set operation permits an optional command to execute after
       setting the pipe buffer sizes. This command is executed with the
       adjusted pipes.

       The --get operation outputs data in a tabular format. The first
       column is the name of the pipe as passed to pipesz. File
       descriptors are named as "fd N". The second column is the size,
       in bytes, of the pipe’s internal buffer. The third column is the
       number of unread bytes currently in the pipe. The columns are
       separated by tabs ('\t', ASCII 09h). If --verbose is specified, a
       descriptive header is also emitted. If neither --file nor --fd
       are specified, --get acts on standard input.

       Unless the --check option is specified, pipesz does not exit if
       it encounters an error while manipulating a file or file
       descriptor. This allows pipesz to be used generically without
       fear of disrupting the execution of pipelines should the type of
       certain files be later changed. For minimal disruption, the
       --quiet option prevents warnings from being emitted in these

       The kernel imposes limits on the amount of pipe buffer space
       unprivileged processes can use, though see BUGS below. The kernel
       will also refuse to shrink a pipe buffer if this would cause a
       loss of buffered data. See pipe(7) for additional details.

       pipesz supports specifying multiple short options consecutively,
       in the usual getopt(3) fashion. The first non-option argument is
       interpreted as command. If command might begin with '-', use '--'
       to separate it from arguments to pipesz. In shell scripts, it is
       good practice to use '--' when parameter expansion is involved.
       pipesz itself does not read from standard input and does not
       write to standard output unless --get, --help, or --version are

OPTIONS         top

       -g, --get
           Report the size of pipe buffers to standard output and exit.
           As a special behavior, if neither --file nor --fd are
           specified, standard input is examined. It is an error to
           specify this option in combination with --set.

       -s, --set size
           Set the size of the pipe buffers, in bytes. This option may
           be suffixed by K, M, G, KiB, MiB, or GiB to indicate
           multiples of 1024. Fractional values are supported in this
           case. Additional suffixes are supported but are unlikely to
           be useful. If this option is not specified, a default value
           is used, as described above. If this option is specified
           multiple times, a warning is emitted and only the
           last-specified size is used. As a special behavior, if
           neither --file nor --fd are specified, standard output is
           adjusted. It is an error to specify this option in
           combination with --get.

       -f, --file path
           Set the buffer size of the FIFO or pipe at path, relative to
           the current working directory. You may specify this option
           multiple times to affect different files, and you may do so
           in combination with --fd. Generally, this option is used with
           FIFOs, but it will also operate on anonymous pipes such as
           those found in /proc/PID/fd. Changes to the buffer size of
           FIFOs are not preserved across system restarts.

       -n, --fd fd
           Set the buffer size of the pipe or FIFO passed to pipesz as
           the specified file descriptor number. You may specify this
           option multiple times to affect different file descriptors,
           and you may do so in combination with --file. Shorthand
           options are provided for the common cases of fd 0 (stdin), fd
           1 (stdout), and fd 2 (stderr). These should suffice in most

       -i, --stdin
           Shorthand for --fd 0.

       -o, --stdout
           Shorthand for --fd 1.

       -e, --stderr
           Shorthand for --fd 2.

       -c, --check
           Exit, without executing command, in case of any error while
           manipulating a file or file descriptor. The default behavior
           if this is not specified is to emit a warning to standard
           error and continue.

       -q, --quiet
           Do not diagnose non-fatal errors to standard error. This
           option does not affect the normal output of --get, --verbose,
           --help, or --version.

       -v, --verbose
           If specified with --get, pipesz will emit a descriptive
           header above the table. Otherwise, if specified, pipesz will
           print the actual buffer sizes set by the kernel to standard

       -h, --help
           Display help text and exit.

       -V, --version
           Print version and exit.

EXAMPLES         top

       pipesz dd if=file bs=1M | ...
           Runs dd(1) with an expanded standard output pipe, allowing it
           to avoid context switches when piping around large blocks.

       pipesz -s1M -cf /run/my-service.fifo
           Sets the pipe buffer size of a service FIFO to 1,048,576
           bytes. If the buffer size could not be set, pipesz exits with
           an error.

       echo hello | pipesz -g
           Prints the size of pipe used by the shell to pass input to
           pipesz. Since pipesz does not read standard input, it may
           also report 6 unread bytes in the pipe, depending on relative

       find /proc/PID/fd -exec pipesz -gqf '{}' ';'
           Prints the size and number of unread bytes of all pipes in
           use by PID. If some pipes are routinely full, pipesz might be
           able to mitigate a processing bottleneck.

NOTES         top

       Linux supports adjusting the size of pipe buffers since kernel
       2.6.35. This release also introduced /proc/sys/fs/pipe-max-size.

       This program uses fcntl(2) F_GETPIPE_SZ/F_SETPIPE_SZ to get and
       set pipe buffer sizes.

       This program uses ioctl(2) FIONREAD to report the amount of
       unread data in pipes. If for some reason this fails, the amount
       of unread data is reported as 0.

BUGS         top

       Before Linux 4.9, some bugs affect how certain resource limits
       are enforced when setting pipe buffer sizes. See pipe(7) for

AUTHORS         top

       Nathan Sharp <nwsharp@live.com>

SEE ALSO         top


REPORTING BUGS         top

       For bug reports, use the issue tracker at

AVAILABILITY         top

       The pipesz command is part of the util-linux package which can be
       downloaded from Linux Kernel Archive
       <https://www.kernel.org/pub/linux/utils/util-linux/>. This page
       is part of the util-linux (a random collection of Linux
       utilities) project. Information about the project can be found at
       ⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩. If you have
       a bug report for this manual page, send it to
       util-linux@vger.kernel.org. This page was obtained from the
       project's upstream Git repository
       ⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
       2023-12-22. (At that time, the date of the most recent commit
       that was found in the repository was 2023-12-14.) If you discover
       any rendering problems in this HTML version of the page, or you
       believe there is a better or more up-to-date source for the page,
       or you have corrections or improvements to the information in
       this COLOPHON (which is not part of the original manual page),
       send a mail to man-pages@man7.org

util-linux 2.39.594-1e0ad      2023-07-19                      PIPESZ(1)