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<title>execline: the ifelse command</title>
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<p>
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<h1> The <tt>ifelse</tt> program </h1>
<p>
<tt>ifelse</tt> performs conditional execution, with two branches.
</p>
<h2> Interface </h2>
<p>
In an <a href="execlineb.html">execlineb</a> script:
</p>
<pre>
ifelse [ -X ] [ -n ] { <em>prog1...</em> } { <em>prog2...</em> } <em>prog3...</em>
</pre>
<ul>
<li> <tt>ifelse</tt> reads <em>prog1...</em> in a
<a href="el_semicolon.html">block</a>. It forks and executes it,
then waits for it to complete. </li>
<li> If <em>prog1</em> crashes, <tt>ifelse</tt> prints an error message
and exits 128 plus the number of the signal that killed <em>prog1</em>. </li>
<li> If <em>prog1</em> exits with a return code equal to 0,
<tt>ifelse</tt> execs into <em>prog2</em>. </li>
<li> Else <tt>ifelse</tt> execs into <em>prog3</em>. </li>
</ul>
<h2> Options </h2>
<ul>
<li> <tt>-n</tt> : negate the test. </li>
<li> <tt>-X</tt> : do not die if <em>prog1</em> crashes; treat a crash
as a non-zero ("false") exit. </li>
</ul>
<h2> Notes </h2>
<ul>
<li> <tt>ifelse <em>prog1...</em> "" <em>prog2...</em> "" <em>prog3...</em></tt> is
roughly equivalent to <tt>sh -c '<em>prog1...</em> && exec <em>prog2...</em> || exec <em>prog3...</em>'</tt>. </li>
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