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<title>s6: the s6-fdholder-getdumpc program</title>
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<h1> The <tt>s6-fdholder-getdumpc</tt> program </h1>
<p>
<tt>s6-fdholder-getdumpc</tt> talks to a
<a href="s6-fdholderd.html">fd-holding daemon</a> on its open
descriptors 6 and 7, and retrieves its whole state,
then executes a program with as many more file descriptors open
as were given by the daemon, plus a modified environment to
describe the retrieved state.
</p>
<h2> Interface </h2>
<pre>
s6-fdholder-getdumpc [ -t <em>timeout</em> ] <em>prog...</em>
</pre>
<ul>
<li> s6-fdholder-getdumpc expects to talk to a listening
<a href="s6-fdholderd.html">s6-fdholderd</a> program on its descriptors 6 and 7. </li>
<li> It retrieves a copy of the whole set of file descriptors
stored in that daemon, including their identifiers and expiration dates. </li>
<li> It then executes into <em>prog...</em> with the additional descriptors
and environment. </li>
</ul>
<h2> Options </h2>
<ul>
<li> <tt>-t <em>timeout</em></tt> : if the operation cannot be
processed in <em>timeout</em> milliseconds, then fail with an error message.
Communications with the server should be near-instant, so this option is
only here to protect users against programming errors. </li>
</ul>
<h2> Environment format </h2>
<p>
<em>prog...</em> is executed with the following environment variables
set:
</p>
<ul>
<li> <tt>S6_FD#</tt> : contains the number <em>n</em> of file
descriptors retrieved from the server. </li>
<li> Then, for every <em>i</em> between 0 and <em>n</em>-1 inclusive:
<ul>
<li> <tt>S6_FD_<em>i</em></tt> : contains the number of the <em>i</em>th
open file descriptor. </li>
<li> <tt>S6_FDID_<em>i</em></tt> : contains the identifier of the
<em>i</em>th open file descriptor. </li>
<li> <tt>S6_FDLIMIT_<em>i</em></tt> : contains the expiration date of
the <em>i</em>th open file descriptor, if applicable. That date is stored in
<a href="http://cr.yp.to/libtai/tai64.html#tai64n">external TAI64N
format</a>. </li>
If the file descriptor is not supposed to expire, that environment variable
is not defined. </li>
</ul> </li>
</ul>
<h2> Notes </h2>
<ul>
<li> s6-fdholder-getdumpc is the "internal" version of
<a href="s6-fdholder-getdump.html">s6-fdholder-getdump</a>. It simply
expects to be run as a UCSPI client, i.e. talking to the server
over descriptors 6 and 7, instead of connecting to the server
itself. </li>
<li> Getting the whole state of a s6-fdholderd daemon requires specific
privileges. Make sure you properly
<a href="s6-fdholderd.html#configuration">configure the s6-fdholderd
access rights</a> so your client can perform that operation. </li>
<li> The error messages for the s6-fdholder suite are explained
<a href="s6-fdholder-errorcodes.html">here</a>. </li>
</ul>
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