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<title>execline: the ifthenelse command</title>
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<p>
<a href="index.html">execline</a><br />
<a href="http://skarnet.org/software/">Software</a><br />
<a href="http://skarnet.org/">skarnet.org</a>
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<h1> The <tt>ifthenelse</tt> program </h1>
<p>
<tt>ifthenelse</tt> performs a conditional alternative.
</p>
<h2> Interface </h2>
<p>
In an <a href="execlineb.html">execlineb</a> script:
</p>
<pre>
ifthenelse [ -X ] [ -s ] { <em>progif...</em> } { <em>progthen...</em> } { <em>progelse...</em> } <em>prog...</em>
</pre>
<ul>
<li> <tt>ifthenelse</tt> reads
<em>progif...</em>, <em>progthen...</em> and <em>progelse...</em> in 3
consecutive <a href="el_semicolon.html">blocks</a>. </li>
<li> <tt>ifthenelse</tt> runs <em>progif...</em> as a child process
and waits for it to complete. </li>
<li> If <em>progif...</em> crashes (i.e. is killed by a signal), <tt>ifthenelse</tt>
prints an error message, then exits 128 plus the number of the signal
that killed <em>progif</em>. </li>
<li> If <em>progif...</em> exits zero, <tt>ifthenelse</tt> runs
<em>progthen...</em> as a child process, else it runs <em>progelse...</em>. </li>
<li> <tt>ifthenelse</tt> waits for its child to complete and puts the exit
status in the <tt>?</tt> environment variable. It then
execs into <em>prog...</em>. </li>
</ul>
<h2> Options </h2>
<ul>
<li> <tt>-X</tt> : if <em>progif</em> crashes, do not exit; proceed
as if it had returned false. </li>
<li> <tt>-s</tt> : magic scoping hack. This option does powerful but
ugly things, and is left undocumented on purpose. </li>
</ul>
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