doc/s6-fghack.html


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    <title>s6: the s6-fghack program</title>
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<h1> The s6-fghack program </h1>

<p>
s6-fghack is an anti-backgrounding tool.
</p>

<h2> Interface </h2>

<pre>
     s6-fghack <em>prog...</em>
</pre>

<ul>
 <li> s6-fghack opens a lot of file descriptors (all writing to a single pipe). </li>
 <li> Then it spawns <em>prog...</em> as a child. </li>
 <li> If something gets written on one of those descriptors, it's a bug in <em>prog</em>.
s6-fghack then complains and exits 102. </li>
 <li> Unless <em>prog...</em> goes out of its way to close descriptors it does not know about,
s6-fghack is able to detect when <em>prog...</em> exits. It exits with an
<a href="//skarnet.org/software/execline/exitcodes.html">approximation</a> of the same exit
code. </li>
</ul>

<h2> Notes </h2>

<p>
 s6-fghack is what it says: a hack. Ideally, you should never have to use it.
It is only useful when you want to supervise a daemon that does not provide a
"stay in the foreground" option; and even then, the right thing is to report
this as a bug to the daemon author and have it fixed.
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