man/sd_event_get_fd.xml

   1 <?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
   4 <!ENTITY % entities SYSTEM "custom-entities.ent" >
   5 %entities;
   6 ]>
   7
   8 <!--
   9   This file is part of systemd.
  10
  11   Copyright 2014 Zbigniew Jędrzejewski-Szmek
  12
  13   systemd is free software; you can redistribute it and/or modify it
  14   under the terms of the GNU Lesser General Public License as published by
  15   the Free Software Foundation; either version 2.1 of the License, or
  16   (at your option) any later version.
  17
  18   systemd is distributed in the hope that it will be useful, but
  19   WITHOUT ANY WARRANTY; without even the implied warranty of
  20   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  21   Lesser General Public License for more details.
  22
  23   You should have received a copy of the GNU Lesser General Public License
  24   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  25 -->
  26
  27 <refentry id="sd_event_get_fd" conditional="ENABLE_KDBUS"
  28         xmlns:xi="http://www.w3.org/2001/XInclude">
  29
  30   <refentryinfo>
  31     <title>sd_event_get_fd</title>
  32     <productname>systemd</productname>
  33
  34     <authorgroup>
  35       <author>
  36         <contrib>More text</contrib>
  37         <firstname>Zbigniew</firstname>
  38         <surname>Jędrzejewski-Szmek</surname>
  39         <email>zbyszek@in.waw.pl</email>
  40       </author>
  41     </authorgroup>
  42   </refentryinfo>
  43
  44   <refmeta>
  45     <refentrytitle>sd_event_get_fd</refentrytitle>
  46     <manvolnum>3</manvolnum>
  47   </refmeta>
  48
  49   <refnamediv>
  50     <refname>sd_event_get_fd</refname>
  51
  52     <refpurpose>Obtain a file descriptor to poll for event loop events</refpurpose>
  53   </refnamediv>
  54
  55   <refsynopsisdiv>
  56     <funcsynopsis>
  57       <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
  58
  59       <funcprototype>
  60         <funcdef>int <function>sd_event_get_fd</function></funcdef>
  61         <paramdef>sd_bus *<parameter>event</parameter></paramdef>
  62       </funcprototype>
  63
  64     </funcsynopsis>
  65   </refsynopsisdiv>
  66
  67   <refsect1>
  68     <title>Description</title>
  69
  70     <para><function>sd_event_get_fd()</function> returns the file
  71     descriptor that the event loop object returned by the
  72     <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  73     function uses to wait for events. This file descriptor can be
  74     polled for events. This makes it possible to embed the
  75     <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  76     event loop inside of another event loop.</para>
  77   </refsect1>
  78
  79   <refsect1>
  80     <title>Return Value</title>
  81
  82     <para>On success, <function>sd_event_get_fd()</function> returns a
  83     non-negative integer. On failure, it returns a negative
  84     errno-style error code.</para>
  85   </refsect1>
  86
  87   <refsect1>
  88     <title>Errors</title>
  89
  90     <para>Returned errors may indicate the following problems:</para>
  91
  92     <variablelist>
  93       <varlistentry>
  94         <term><constant>-EINVAL</constant></term>
  95
  96         <listitem><para><parameter>event</parameter> is not a valid
  97         pointer to an <structname>sd_event</structname> structure.
  98         </para></listitem>
  99       </varlistentry>
 100
 101       <varlistentry>
 102         <term><constant>-ECHILD</constant></term>
 103
 104         <listitem><para>The event loop has been created in a different process.</para></listitem>
 105
 106       </varlistentry>
 107     </variablelist>
 108   </refsect1>
 109
 110   <refsect1>
 111     <title>Examples</title>
 112
 113     <example>
 114       <title>Integration in glib event loop</title>
 115
 116       <programlisting><xi:include href="glib-event-glue.c" parse="text" /></programlisting>
 117     </example>
 118   </refsect1>
 119
 120   <refsect1>
 121     <title>Notes</title>
 122
 123     <para><function>sd_event_get_fd()</function> is available as a
 124     shared library, which can be compiled and linked to with the
 125     <constant>libsystemd</constant> <citerefentry
 126     project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 127     file.</para>
 128   </refsect1>
 129
 130   <refsect1>
 131     <title>See Also</title>
 132
 133     <para>
 134       <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 135       <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 136       <citerefentry><refentrytitle>sd_event_ref</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 137     </para>
 138   </refsect1>
 139
 140 </refentry>