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<title>execline: the fdmove program</title>
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<a href="index.html">execline</a><br />
<a href="//skarnet.org/software/">Software</a><br />
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<h1> The <tt>fdmove</tt> program </h1>
<p>
<tt>fdmove</tt> moves or copies a given file descriptor, then
executes a program.
</p>
<h2> Interface </h2>
<pre>
fdmove [ -c ] <em>fdto</em> <em>fdfrom</em> <em>prog...</em>
</pre>
<p>
<tt>fdmove</tt> moves the file descriptor number <em>fdfrom</em>,
to number <em>fdto</em>, then execs into <em>prog</em> with its arguments.
If <em>fdto</em> is open, <tt>fdmove</tt> closes it before moving
<em>fdfrom</em> to it.
</p>
<h2> Options </h2>
<ul>
<li> <tt>-c</tt> : duplicate <em>fdfrom</em> to <em>fdto</em>
instead of moving it; do not close <em>fdfrom</em>. </li>
</ul>
<h2> Notes </h2>
<ul>
<li> <tt>fdmove <em>a</em> <em>b</em> prog...</tt> is roughly equivalent to
<tt>sh -c 'exec prog... <em>a</em>>&<em>b</em> <em>b</em><&-'</tt>.
It means: if you write to fd <em>a</em> now, it will have the same effect as writing
to fd <em>b</em> beforehand, and you cannot write to fd <em>b</em> anymore. </li>
<li> <tt>fdmove -c <em>a</em> <em>b</em> prog...</tt> is roughly equivalent to
<tt>sh -c 'exec prog... <em>a</em>>&<em>b</em>'</tt>. It means: you can
now write to fd <em>a</em>, and also still write to fd <em>b</em>, and both will have
the same effect as writing to fd <em>b</em> beforehand. </li>
<li> It also works with file descriptors that are open for reading! </li>
</ul>
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