209 lines
12 KiB
HTML
209 lines
12 KiB
HTML
<!DOCTYPE html>
|
|
<html>
|
|
<!-- Created by GNU Texinfo 7.1, https://www.gnu.org/software/texinfo/ -->
|
|
<head>
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
|
|
<!-- This manual documents Guile version 3.0.10.
|
|
|
|
Copyright (C) 1996-1997, 2000-2005, 2009-2023 Free Software Foundation,
|
|
Inc.
|
|
|
|
Copyright (C) 2021 Maxime Devos
|
|
|
|
Copyright (C) 2024 Tomas Volf
|
|
|
|
|
|
Permission is granted to copy, distribute and/or modify this document
|
|
under the terms of the GNU Free Documentation License, Version 1.3 or
|
|
any later version published by the Free Software Foundation; with no
|
|
Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A
|
|
copy of the license is included in the section entitled "GNU Free
|
|
Documentation License." -->
|
|
<title>Pipes (Guile Reference Manual)</title>
|
|
|
|
<meta name="description" content="Pipes (Guile Reference Manual)">
|
|
<meta name="keywords" content="Pipes (Guile Reference Manual)">
|
|
<meta name="resource-type" content="document">
|
|
<meta name="distribution" content="global">
|
|
<meta name="Generator" content=".texi2any-real">
|
|
<meta name="viewport" content="width=device-width,initial-scale=1">
|
|
|
|
<link href="index.html" rel="start" title="Top">
|
|
<link href="Concept-Index.html" rel="index" title="Concept Index">
|
|
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
|
|
<link href="POSIX.html" rel="up" title="POSIX">
|
|
<link href="Networking.html" rel="next" title="Networking">
|
|
<link href="Terminals-and-Ptys.html" rel="prev" title="Terminals and Ptys">
|
|
<style type="text/css">
|
|
<!--
|
|
a.copiable-link {visibility: hidden; text-decoration: none; line-height: 0em}
|
|
div.example {margin-left: 3.2em}
|
|
span:hover a.copiable-link {visibility: visible}
|
|
strong.def-name {font-family: monospace; font-weight: bold; font-size: larger}
|
|
-->
|
|
</style>
|
|
<link rel="stylesheet" type="text/css" href="https://www.gnu.org/software/gnulib/manual.css">
|
|
|
|
|
|
</head>
|
|
|
|
<body lang="en">
|
|
<div class="subsection-level-extent" id="Pipes">
|
|
<div class="nav-panel">
|
|
<p>
|
|
Next: <a href="Networking.html" accesskey="n" rel="next">Networking</a>, Previous: <a href="Terminals-and-Ptys.html" accesskey="p" rel="prev">Terminals and Ptys</a>, Up: <a href="POSIX.html" accesskey="u" rel="up"><abbr class="acronym">POSIX</abbr> System Calls and Networking</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
|
|
</div>
|
|
<hr>
|
|
<h4 class="subsection" id="Pipes-1"><span>7.2.10 Pipes<a class="copiable-link" href="#Pipes-1"> ¶</a></span></h4>
|
|
<a class="index-entry-id" id="index-pipe-1"></a>
|
|
|
|
<p>The following procedures are similar to the <code class="code">popen</code> and
|
|
<code class="code">pclose</code> system routines. The code is in a separate “popen”
|
|
module<a class="footnote" id="DOCF24" href="#FOOT24"><sup>24</sup></a>:
|
|
</p>
|
|
<div class="example lisp">
|
|
<pre class="lisp-preformatted">(use-modules (ice-9 popen))
|
|
</pre></div>
|
|
|
|
<a class="index-entry-id" id="index-popen"></a>
|
|
<dl class="first-deffn">
|
|
<dt class="deffn" id="index-open_002dpipe"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">open-pipe</strong> <var class="def-var-arguments">command mode</var><a class="copiable-link" href="#index-open_002dpipe"> ¶</a></span></dt>
|
|
<dt class="deffnx def-cmd-deffn" id="index-open_002dpipe_002a"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">open-pipe*</strong> <var class="def-var-arguments">mode prog [args...]</var><a class="copiable-link" href="#index-open_002dpipe_002a"> ¶</a></span></dt>
|
|
<dd><p>Execute a command in a subprocess, with a pipe to it or from it, or
|
|
with pipes in both directions.
|
|
</p>
|
|
<p><code class="code">open-pipe</code> runs the shell <var class="var">command</var> using ‘<samp class="samp">/bin/sh -c</samp>’.
|
|
<code class="code">open-pipe*</code> executes <var class="var">prog</var> directly, with the optional
|
|
<var class="var">args</var> arguments (all strings).
|
|
</p>
|
|
<p><var class="var">mode</var> should be one of the following values. <code class="code">OPEN_READ</code> is
|
|
an input pipe, ie. to read from the subprocess. <code class="code">OPEN_WRITE</code>
|
|
is an output pipe, ie. to write to it.
|
|
</p>
|
|
<dl class="first-defvr first-defvar-alias-first-defvr">
|
|
<dt class="defvr defvar-alias-defvr" id="index-OPEN_005fREAD"><span class="category-def">Variable: </span><span><strong class="def-name">OPEN_READ</strong><a class="copiable-link" href="#index-OPEN_005fREAD"> ¶</a></span></dt>
|
|
<dt class="defvrx defvarx-alias-defvrx def-cmd-defvr" id="index-OPEN_005fWRITE"><span class="category-def">Variable: </span><span><strong class="def-name">OPEN_WRITE</strong><a class="copiable-link" href="#index-OPEN_005fWRITE"> ¶</a></span></dt>
|
|
<dt class="defvrx defvarx-alias-defvrx def-cmd-defvr" id="index-OPEN_005fBOTH"><span class="category-def">Variable: </span><span><strong class="def-name">OPEN_BOTH</strong><a class="copiable-link" href="#index-OPEN_005fBOTH"> ¶</a></span></dt>
|
|
</dl>
|
|
|
|
<p>For an input pipe, the child’s standard output is the pipe and
|
|
standard input is inherited from <code class="code">current-input-port</code>. For an
|
|
output pipe, the child’s standard input is the pipe and standard
|
|
output is inherited from <code class="code">current-output-port</code>. In all cases
|
|
the child’s standard error is inherited from
|
|
<code class="code">current-error-port</code> (see <a class="pxref" href="Default-Ports.html">Default Ports for Input, Output and Errors</a>).
|
|
</p>
|
|
<p>If those <code class="code">current-X-ports</code> are not files of some kind, and hence
|
|
don’t have file descriptors for the child, then <samp class="file">/dev/null</samp> is
|
|
used instead.
|
|
</p>
|
|
<p>Care should be taken with <code class="code">OPEN_BOTH</code>, a deadlock will occur if
|
|
both parent and child are writing, and waiting until the write completes
|
|
before doing any reading. Each direction has <code class="code">PIPE_BUF</code> bytes of
|
|
buffering (see <a class="pxref" href="Buffering.html">Buffering</a>), which will be enough for small writes,
|
|
but not for say putting a big file through a filter.
|
|
</p></dd></dl>
|
|
|
|
<dl class="first-deffn">
|
|
<dt class="deffn" id="index-open_002dinput_002dpipe"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">open-input-pipe</strong> <var class="def-var-arguments">command</var><a class="copiable-link" href="#index-open_002dinput_002dpipe"> ¶</a></span></dt>
|
|
<dd><p>Equivalent to <code class="code">open-pipe</code> with mode <code class="code">OPEN_READ</code>.
|
|
</p>
|
|
<div class="example lisp">
|
|
<pre class="lisp-preformatted">(let* ((port (open-input-pipe "date --utc"))
|
|
(str (read-line port))) ; from (ice-9 rdelim)
|
|
(close-pipe port)
|
|
str)
|
|
⇒ "Mon Mar 11 20:10:44 UTC 2002"
|
|
</pre></div>
|
|
</dd></dl>
|
|
|
|
<dl class="first-deffn">
|
|
<dt class="deffn" id="index-open_002doutput_002dpipe"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">open-output-pipe</strong> <var class="def-var-arguments">command</var><a class="copiable-link" href="#index-open_002doutput_002dpipe"> ¶</a></span></dt>
|
|
<dd><p>Equivalent to <code class="code">open-pipe</code> with mode <code class="code">OPEN_WRITE</code>.
|
|
</p>
|
|
<div class="example lisp">
|
|
<pre class="lisp-preformatted">(let ((port (open-output-pipe "lpr")))
|
|
(display "Something for the line printer.\n" port)
|
|
(if (not (eqv? 0 (status:exit-val (close-pipe port))))
|
|
(error "Cannot print")))
|
|
</pre></div>
|
|
</dd></dl>
|
|
|
|
<dl class="first-deffn">
|
|
<dt class="deffn" id="index-open_002dinput_002doutput_002dpipe"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">open-input-output-pipe</strong> <var class="def-var-arguments">command</var><a class="copiable-link" href="#index-open_002dinput_002doutput_002dpipe"> ¶</a></span></dt>
|
|
<dd><p>Equivalent to <code class="code">open-pipe</code> with mode <code class="code">OPEN_BOTH</code>.
|
|
</p></dd></dl>
|
|
|
|
<a class="index-entry-id" id="index-pclose"></a>
|
|
<dl class="first-deffn">
|
|
<dt class="deffn" id="index-close_002dpipe"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">close-pipe</strong> <var class="def-var-arguments">port</var><a class="copiable-link" href="#index-close_002dpipe"> ¶</a></span></dt>
|
|
<dd><p>Close a pipe created by <code class="code">open-pipe</code>, wait for the process to
|
|
terminate, and return the wait status code. The status is as per
|
|
<code class="code">waitpid</code> and can be decoded with <code class="code">status:exit-val</code> etc
|
|
(see <a class="pxref" href="Processes.html">Processes</a>)
|
|
</p></dd></dl>
|
|
|
|
<br>
|
|
<p><code class="code">waitpid WAIT_ANY</code> should not be used when pipes are open, since
|
|
it can reap a pipe’s child process, causing an error from a subsequent
|
|
<code class="code">close-pipe</code>.
|
|
</p>
|
|
<p><code class="code">close-port</code> (see <a class="pxref" href="Ports.html">Ports</a>) can close a pipe, but it doesn’t reap
|
|
the child process.
|
|
</p>
|
|
<p>The garbage collector will close a pipe no longer in use, and reap the
|
|
child process with <code class="code">waitpid</code>. If the child hasn’t yet terminated
|
|
the garbage collector doesn’t block, but instead checks again in the
|
|
next GC.
|
|
</p>
|
|
<p>Many systems have per-user and system-wide limits on the number of
|
|
processes, and a system-wide limit on the number of pipes, so pipes
|
|
should be closed explicitly when no longer needed, rather than letting
|
|
the garbage collector pick them up at some later time.
|
|
</p>
|
|
<dl class="first-deffn">
|
|
<dt class="deffn" id="index-pipeline"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">pipeline</strong> <var class="def-var-arguments"><var class="var">commands</var></var><a class="copiable-link" href="#index-pipeline"> ¶</a></span></dt>
|
|
<dd><p>Execute a pipeline of <var class="var">commands</var>, where each command is a
|
|
list of a program and its arguments as strings, returning an input
|
|
port to the end of the pipeline, an output port to the beginning of the
|
|
pipeline and a list of PIDs of the processes executing the <var class="var">commands</var>.
|
|
</p>
|
|
<div class="example">
|
|
<pre class="example-preformatted">(let ((commands '(("git" "ls-files")
|
|
("tar" "-cf-" "-T-")
|
|
("sha1sum" "-")))
|
|
(success? (lambda (pid)
|
|
(zero?
|
|
(status:exit-val (cdr (waitpid pid)))))))
|
|
(receive (from to pids) (pipeline commands)
|
|
(let* ((sha1 (read-delimited " " from))
|
|
(index (list-index (negate success?) (reverse pids))))
|
|
(close to)
|
|
(close from)
|
|
(if (not index)
|
|
sha1
|
|
(string-append "pipeline failed in command: "
|
|
(string-join (list-ref commands index)))))))
|
|
⇒ "52f99d234503fca8c84ef94b1005a3a28d8b3bc1"
|
|
</pre></div>
|
|
</dd></dl>
|
|
|
|
</div>
|
|
<div class="footnotes-segment">
|
|
<hr>
|
|
<h4 class="footnotes-heading">Footnotes</h4>
|
|
|
|
<h5 class="footnote-body-heading"><a id="FOOT24" href="#DOCF24">(24)</a></h5>
|
|
<p>This module is only available on systems where the
|
|
<code class="code">popen</code> feature is provided (see <a class="pxref" href="Common-Feature-Symbols.html">Common Feature Symbols</a>).</p>
|
|
</div>
|
|
<hr>
|
|
<div class="nav-panel">
|
|
<p>
|
|
Next: <a href="Networking.html">Networking</a>, Previous: <a href="Terminals-and-Ptys.html">Terminals and Ptys</a>, Up: <a href="POSIX.html"><abbr class="acronym">POSIX</abbr> System Calls and Networking</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
|
|
</div>
|
|
|
|
|
|
|
|
</body>
|
|
</html>
|