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<title>execline: the tryexec 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>
</p>
<h1> The <tt>tryexec</tt> program </h1>
<p>
<tt>tryexec</tt> executes into a command line, with a fallback.
</p>
<h2> Interface </h2>
<p>
In an <a href="execlineb.html">execlineb</a> script:
</p>
<pre>
tryexec [ -n ] [ -c ] [ -l ] [ -a argv0 ] { <em>prog1...</em> } <em>prog2...</em>
</pre>
<ul>
<li> <tt>tryexec</tt> reads <em>prog1...</em> in a
<a href="el_semicolon.html">block</a>. It then executes into it,
completely forgetting <em>prog2...</em> </li>
<li> If for some reason the <tt>execve()</tt> fails - for instance,
a non-executable <em>prog1</em> - then <tt>tryexec</tt> executes
into <em>prog2...</em> instead. </li>
</ul>
<h2> Options </h2>
<ul>
<li> <tt>-n</tt> : reverse <em>prog1...</em> and <em>prog2...</em>'s
role. The latter becomes the main execution path and the former becomes
the fallback. </li>
</ul>
<p>
The <tt>-c</tt>, <tt>-l</tt> and <tt>-a</tt> options have the same
semantics as with the <a href="exec.html">exec</a> program.
</p>
<h2> Notes </h2>
<ul>
<li> <tt>tryexec <em>prog1...</em> "" <em>prog2...</em></tt> would be
equivalent to
<tt>sh -c 'exec <em>prog1...</em> || exec <em>prog2...</em>'</tt>, if
such a shell construct existed. Unfortunately, the shell language does
not offer that functionality. </li>
</ul>
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