1PIPESZ(1) User Commands PIPESZ(1)
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6 pipesz - set or examine pipe and FIFO buffer sizes
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9 pipesz [options] [--set size] [--] [command [argument] ...]
10 pipesz [options] --get
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14 Pipes and FIFOs maintain an internal buffer used to transfer data
15 between the read end and the write end. In some cases, the default size
16 of this internal buffer may not be appropriate. This program provides
17 facilities to set and examine the size of these buffers.
18 The --set operation sets pipe buffer sizes. If it is specified, it must
20 be specified with an explicit size. Otherwise, it is implied and the
21 size is read from /proc/sys/fs/pipe-max-size. The kernel may adjust
22 size as described in fcntl(2). To determine the actual buffer sizes
23 set, use the --verbose option. If neither --file nor --fd are
24 specified, --set acts on standard output.
25 The --set operation permits an optional command to execute after
27 setting the pipe buffer sizes. This command is executed with the
28 adjusted pipes.
29 The --get operation outputs data in a tabular format. The first column
31 is the name of the pipe as passed to pipesz. File descriptors are named
32 as "fd N". The second column is the size, in bytes, of the pipe’s
33 internal buffer. The third column is the number of unread bytes
34 currently in the pipe. The columns are separated by tabs ('\t', ASCII
35 09h). If --verbose is specified, a descriptive header is also emitted.
36 If neither --file nor --fd are specified, --get acts on standard input.
37 Unless the --check option is specified, pipesz does not exit if it
39 encounters an error while manipulating a file or file descriptor. This
40 allows pipesz to be used generically without fear of disrupting the
41 execution of pipelines should the type of certain files be later
42 changed. For minimal disruption, the --quiet option prevents warnings
43 from being emitted in these cases.
44 The kernel imposes limits on the amount of pipe buffer space
46 unprivileged processes can use, though see BUGS below. The kernel will
47 also refuse to shrink a pipe buffer if this would cause a loss of
48 buffered data. See pipe(7) for additional details.
49 pipesz supports specifying multiple short options consecutively, in the
51 usual getopt(3) fashion. The first non-option argument is interpreted
52 as command. If command might begin with '-', use '--' to separate it
53 from arguments to pipesz. In shell scripts, it is good practice to use
54 '--' when parameter expansion is involved. pipesz itself does not read
55 from standard input and does not write to standard output unless --get,
56 --help, or --version are specified.
57
59 -g, --get
60 Report the size of pipe buffers to standard output and exit. As a
61 special behavior, if neither --file nor --fd are specified,
62 standard input is examined. It is an error to specify this option
63 in combination with --set.
64 -s, --set size
66 Set the size of the pipe buffers, in bytes. This option may be
67 suffixed by K, M, G, KiB, MiB, or GiB to indicate multiples of
68 1024. Fractional values are supported in this case. Additional
69 suffixes are supported but are unlikely to be useful. If this
70 option is not specified, a default value is used, as described
71 above. If this option is specified multiple times, a warning is
72 emitted and only the last-specified size is used. As a special
73 behavior, if neither --file nor --fd are specified, standard output
74 is adjusted. It is an error to specify this option in combination
75 with --get.
76 -f, --file path
78 Set the buffer size of the FIFO or pipe at path, relative to the
79 current working directory. You may specify this option multiple
80 times to affect different files, and you may do so in combination
81 with --fd. Generally, this option is used with FIFOs, but it will
82 also operate on anonymous pipes such as those found in
83 /proc/PID/fd. Changes to the buffer size of FIFOs are not preserved
84 across system restarts.
85 -n, --fd fd
87 Set the buffer size of the pipe or FIFO passed to pipesz as the
88 specified file descriptor number. You may specify this option
89 multiple times to affect different file descriptors, and you may do
90 so in combination with --file. Shorthand options are provided for
91 the common cases of fd 0 (stdin), fd 1 (stdout), and fd 2 (stderr).
92 These should suffice in most cases.
93 -i, --stdin
95 Shorthand for --fd 0.
96 -o, --stdout
98 Shorthand for --fd 1.
99 -e, --stderr
101 Shorthand for --fd 2.
102 -c, --check
104 Exit, without executing command, in case of any error while
105 manipulating a file or file descriptor. The default behavior if
106 this is not specified is to emit a warning to standard error and
107 continue.
108 -q, --quiet
110 Do not diagnose non-fatal errors to standard error. This option
111 does not affect the normal output of --get, --verbose, --help, or
112 --version.
113 -v, --verbose
115 If specified with --get, pipesz will emit a descriptive header
116 above the table. Otherwise, if specified, pipesz will print the
117 actual buffer sizes set by the kernel to standard error.
118 -h, --help
120 Display help text and exit.
121 -V, --version
123 Print version and exit.
124
126 pipesz dd if=file bs=1M | ...
127 Runs dd(1) with an expanded standard output pipe, allowing it to
128 avoid context switches when piping around large blocks.
129 pipesz -s1M -cf /run/my-service.fifo
131 Sets the pipe buffer size of a service FIFO to 1,048,576 bytes. If
132 the buffer size could not be set, pipesz exits with an error.
133 echo hello | pipesz -g
135 Prints the size of pipe used by the shell to pass input to pipesz.
136 Since pipesz does not read standard input, it may also report 6
137 unread bytes in the pipe, depending on relative timings.
138 find /proc/PID/fd -exec pipesz -gqf '{}' ';'
140 Prints the size and number of unread bytes of all pipes in use by
141 PID. If some pipes are routinely full, pipesz might be able to
142 mitigate a processing bottleneck.
143
145 Linux supports adjusting the size of pipe buffers since kernel 2.6.35.
146 This release also introduced /proc/sys/fs/pipe-max-size.
147 This program uses fcntl(2) F_GETPIPE_SZ/F_SETPIPE_SZ to get and set
149 pipe buffer sizes.
150 This program uses ioctl(2) FIONREAD to report the amount of unread data
152 in pipes. If for some reason this fails, the amount of unread data is
153 reported as 0.
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156 Before Linux 4.9, some bugs affect how certain resource limits are
157 enforced when setting pipe buffer sizes. See pipe(7) for details.
158
160 Nathan Sharp <nwsharp@live.com>
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163 pipe(7)
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166 For bug reports, use the issue tracker at
167 https://github.com/util-linux/util-linux/issues.
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170 The pipesz command is part of the util-linux package which can be
171 downloaded from Linux Kernel Archive
172 <https://www.kernel.org/pub/linux/utils/util-linux/>.
173util-linux 2.39.2 2023-06-14 PIPESZ(1)