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diff --git a/doc/s6-fdholder-retrieve.html b/doc/s6-fdholder-retrieve.html new file mode 100644 index 0000000..5231051 --- /dev/null +++ b/doc/s6-fdholder-retrieve.html @@ -0,0 +1,98 @@ +<html> + <head> + <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> + <meta http-equiv="Content-Language" content="en" /> + <title>s6: the s6-fdholder-retrieve program</title> + <meta name="Description" content="s6: the s6-fdholder-retrieve program" /> + <meta name="Keywords" content="s6 s6-fdholder fd-holding fd-holder fd retrieval unix socket activation" /> + <!-- <link rel="stylesheet" type="text/css" href="http://skarnet.org/default.css" /> --> + </head> +<body> + +<p> +<a href="index.html">s6</a><br /> +<a href="http://skarnet.org/software/">Software</a><br /> +<a href="http://skarnet.org/">skarnet.org</a> +</p> + +<h1> The <tt>s6-fdholder-retrieve</tt> program </h1> + +<p> +<tt>s6-fdholder-retrieve</tt> connects to a +<a href="s6-fdholderd.html">fd-holding daemon</a> listening on a +Unix domain socket, and retrieves a file descriptor from that +daemon, then executes a program with that file descriptor as the +program's standard input. +</p> + +<h2> Interface </h2> + +<pre> + s6-fdholder-retrieve [ -D ] [ -t <em>timeout</em> ] <em>path</em> <em>id</em> <em>prog...</em> +</pre> + +<ul> + <li> s6-fdholder-retrieve executes into <tt><a href="s6-ipcclient.html">s6-ipcclient</a> <em>path</em> +<a href="s6-fdholder-retrievec.html">s6-fdholder-retrievec</a> <em>id</em> <em>prog...</em></tt>. +It does nothing else: it is just a convenience program. +The <a href="s6-ipcclient.html">s6-ipcclient</a> program connects +to a Unix socket at <em>path</em>, and the +<a href="s6-fdholder-retrievec.html">s6-fdholder-retrievec</a> program +gets the file descriptor identified by <em>id</em> over the socket. </li> + <li> It should be used to connect to a +<a href="s6-fdholderd.html">s6-fdholderd</a> daemon, which will pass the +file descriptor to the client over the <em>path</em> socket. </li> + <li> It executes into <em>prog...</em> with the retrieved file +descriptor as <em>prog...</em>'s standard input. </li> +</ul> + +<h2> Options </h2> + +<ul> + <li> <tt>-D</tt> : delete the file descriptor from the server's +storage after retrieval. This option requires writing rights over the +given identifier as well as reading rights: check the server's +<a href="s6-fdholderd.html#configuration">configuration</a>. </li> + <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 (connecting to the +wrong socket, for instance). </li> +</ul> + +<h2> Usage example </h2> + +<pre> + s6-fdholder-store /service/fdholderd/s MYSOCKET s6-ipcserverd cat +</pre> + +<p> + will retrieve a file descriptor stored under the MYSOCKET identifier in +the s6-fdholderd daemon listening on the <tt>/service/fdholderd/s</tt> +socket, and execute into <tt>s6-ipcserverd cat</tt> with that file +descriptor as stdin. In this case, if MYSOCKET referred to a Unix domain +socket, <a href="s6-ipcserverd.html">s6-ipcserverd</a> will then accept +client connections on it and spawn a <tt>cat</tt> program for every +connection. +</p> + +<h2> Notes </h2> + +<ul> + <li> s6-fdholder-retrieve really executes into <tt>s6-ipcclient +s6-fdholder-retrievec +<a href="http://skarnet.org/software/execline/fdclose.html">fdclose</a> +6 fdclose 7 <em>prog...</em></tt>, so that <em>prog...</em> does not +have a connection with the fd-holding daemon anymore. If you want to +keep the server connection open for <em>prog...</em>, use +<tt>s6-ipcclient s6-fdholder-retrievec</tt> manually. </li> + <li> To execute <em>prog</em> with the newly retrieved file descriptor +as number <em>n</em> while preserving stdin, use the following construct: +<tt>fdmove <em>n</em> 0 s6-fdholder-retrieve <em>path</em> <em>id</em> +<a href="http://skarnet.org/software/execline/fdswap.html">fdswap</a> +0 <em>n</em> <em>prog...</em></tt>. Be aware that <em>n</em> +cannot be 6 or 7, internally used by s6-fdholder-retrieve. </li> +</ul> + +</body> +</html> |