<html><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968"><title>ext:run-program</title><link rel="stylesheet" href="ecl.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.75.2"><link rel="home" href="index.html" title="The ECL manual"><link rel="up" href="ch17s03.html" title="2.3. OS Reference"><link rel="prev" href="re10.html" title="ext:quit"><link rel="next" href="re12.html" title="ext:system"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><code class="function">ext:run-program</code></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="re10.html">Prev</a> </td><th width="60%" align="center">2.3. OS Reference</th><td width="20%" align="right"> <a accesskey="n" href="re12.html">Next</a></td></tr></table><hr></div><div class="refentry" title="ext:run-program"><a name="ref.run-program"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p><code class="function">ext:run-program</code> — Start and communicate with a child process.</p></div><div class="refsynopsisdiv" title="Function"><h2>Function</h2><div class="funcsynopsis"><p><code class="funcdef">(ext:run-program</code> <var class="pdparam">command</var>) ⇒ <var class="pdparam">argv</var>) ⇒ &key) ⇒ input) ⇒ output) ⇒ error)</p></div><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><p><span class="term"><em class="replaceable"><code>input</code></em></span></p></td><td><p>One of <span class="symbol">:STREAM</span>, <span class="symbol">T</span> or
<span class="symbol">NIL</span>, defaults to
<span class="symbol">:STREAM</span></p></td></tr><tr><td><p><span class="term"><em class="replaceable"><code>output</code></em></span></p></td><td><p>One of <span class="symbol">:STREAM</span>, <span class="symbol">T</span> or
<span class="symbol">NIL</span>, defaults to
<span class="symbol">:STREAM</span></p></td></tr><tr><td><p><span class="term"><em class="replaceable"><code>error</code></em></span></p></td><td><p>One of <span class="symbol">:OUTPUT</span>, <span class="symbol">T</span> or
<span class="symbol">NIL</span>, defaults to
<span class="symbol">:STREAM</span></p></td></tr></tbody></table></div></div><div class="refsect1" title="Description"><a name="id654545"></a><h2>Description</h2><p>This function creates a external process by launching the program
<em class="replaceable"><code>command</code></em> with the arguments from the list
<em class="replaceable"><code>argv</code></em>.</p><p>The arguments <em class="replaceable"><code>input</code></em>,
<em class="replaceable"><code>output</code></em> and <em class="replaceable"><code>error</code></em> are
used to intercept the standard input, output and error streams of the
program. A value of <span class="symbol">:STREAM</span> means a lisp stream will be
created to communicate with the child process. A value of
<span class="symbol">NIL</span> means that the data from this pipe will be
discarded. The vaule of <span class="symbol">T</span> means that the child process will
use the parent's standard input, output or error channels. For instance, if
<span class="application">ECL</span> writes to the console and you pass a value of
<em class="replaceable"><code>output</code></em> equal to <span class="symbol">:STREAM</span>, the
child process will also output to the console. Finally, the error messages
of the child process are redirected to the same pipe as its standard
output when <em class="replaceable"><code>error</code></em> takes the value
<span class="symbol">:OUTPUT</span>.</p><p>If the child process was succesfully launched, this function outputs a
lisp stream to which we one may write, read or do both things, depending on
the arguments <em class="replaceable"><code>input</code></em> and
<em class="replaceable"><code>output</code></em>. If an error happened during the
preparation of the child process (for instance the program was not found),
this function returns <em class="replaceable"><code>NIL</code></em>.</p><p>The design of this function is inspired by the function of same name
in <span class="application">CMUCL</span> and <span class="application">SBCL</span>.</p></div><div class="refsect1" title="Example"><a name="id654641"></a><h2>Example</h2><p>List all users in a Unix system. We use the <span class="command"><strong>sed</strong></span>
command to parse the file with the list of users, removing comments and
information other than the user names:
</p><pre class="programlisting">(defun all-users (&optional (file "/etc/passwd"))
(let ((s (ext:run-program "sed"
(list "-e" "/^#.*$/d;/^[^:]*$/d;s,^\\([^:]*\\).*$,\\1,g"
file)
:input NIL :output :STREAM :error NIL)))
(unless s
(error "Unable to parse password file"))
(loop for x = (read s NIL NIL)
while x
collect x)))</pre><p>Make a directory. Redirect standard error output to the same as the
output:
</p><pre class="programlisting">(ext:run-program "mkdir" '("./tmp") :output :STREAM :error :OUTPUT)
</pre><p>
</p><p>Same as before, but now both the output and the standard error are
discarded
</p><pre class="programlisting">(ext:run-program "mkdir" '("./tmp") :output NIL :error :OUTPUT)
</pre><p>
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