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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | NOTES | BUGS | AUTHORS | SEE ALSO | REPORTING BUGS | AVAILABILITY |
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PIPESZ(1) User Commands PIPESZ(1)
pipesz - set or examine pipe and FIFO buffer sizes
pipesz [options] [--set size] [--] [command [argument] ...]
pipesz [options] --get
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
buffers.
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
cases.
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
specified.
-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
cases.
-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
error.
-h, --help
Display help text and exit.
-V, --version
Print version and exit.
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
timings.
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.
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.
Before Linux 4.9, some bugs affect how certain resource limits
are enforced when setting pipe buffer sizes. See pipe(7) for
details.
Nathan Sharp <[email protected]>
pipe(7)
For bug reports, use the issue tracker at
https://github.com/util-linux/util-linux/issues.
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
[email protected]. This page was obtained from the
project's upstream Git repository
⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
2024-06-14. (At that time, the date of the most recent commit
that was found in the repository was 2024-06-10.) 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 [email protected]
util-linux 2.39.594-1e0ad 2023-07-19 PIPESZ(1)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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