man/sd_event_exit.xml

   1 <?xml version='1.0'?>
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
   4 <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
   5
   6 <refentry id="sd_event_exit" xmlns:xi="http://www.w3.org/2001/XInclude">
   7
   8   <refentryinfo>
   9     <title>sd_event_exit</title>
  10     <productname>systemd</productname>
  11   </refentryinfo>
  12
  13   <refmeta>
  14     <refentrytitle>sd_event_exit</refentrytitle>
  15     <manvolnum>3</manvolnum>
  16   </refmeta>
  17
  18   <refnamediv>
  19     <refname>sd_event_exit</refname>
  20     <refname>sd_event_get_exit_code</refname>
  21
  22     <refpurpose>Ask the event loop to exit</refpurpose>
  23   </refnamediv>
  24
  25   <refsynopsisdiv>
  26     <funcsynopsis>
  27       <funcsynopsisinfo>#include &lt;systemd/sd-event.h&gt;</funcsynopsisinfo>
  28
  29       <funcprototype>
  30         <funcdef>int <function>sd_event_exit</function></funcdef>
  31         <paramdef>sd_event *<parameter>event</parameter></paramdef>
  32         <paramdef>int <parameter>code</parameter></paramdef>
  33       </funcprototype>
  34
  35       <funcprototype>
  36         <funcdef>int <function>sd_event_get_exit_code</function></funcdef>
  37         <paramdef>sd_event *<parameter>event</parameter></paramdef>
  38         <paramdef>int *<parameter>code</parameter></paramdef>
  39       </funcprototype>
  40
  41     </funcsynopsis>
  42   </refsynopsisdiv>
  43
  44   <refsect1>
  45     <title>Description</title>
  46
  47     <para><function>sd_event_exit()</function> requests the event loop
  48     specified in the <parameter>event</parameter> event loop object to
  49     exit. The <parameter>code</parameter> parameter may be any integer
  50     value and is returned as-is by
  51     <citerefentry><refentrytitle>sd_event_loop</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  52     after the last event loop iteration. It may also be queried
  53     using <function>sd_event_get_exit_code()</function>, see
  54     below. </para>
  55
  56     <para>When exiting is requested the event loop will stop listening
  57     for and dispatching regular event sources. Instead it will proceed
  58     with executing only event sources registered with
  59     <citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  60     in the order defined by their priority. After all exit event
  61     sources have been dispatched the event loop is terminated.</para>
  62
  63     <para>If <function>sd_event_exit()</function> is invoked a second
  64     time while the event loop is still processing exit event sources,
  65     the exit code stored in the event loop object is updated, but
  66     otherwise no further operation is executed.</para>
  67
  68     <para><function>sd_event_get_exit_code()</function> may be used to query the exit code passed to an
  69     earlier call of <function>sd_event_exit()</function>. The return parameter <parameter>code</parameter>
  70     may be set to <constant>NULL</constant>, in order to simply check if <function>sd_event_exit()</function>
  71     has been called before (as <function>sd_event_get_exit_code()</function> fails with
  72     <constant>-ENODATA</constant> if that's not the case, see below).</para>
  73
  74     <para>While the full positive and negative integer ranges may be used
  75     for the exit code, care should be taken not pick exit codes that
  76     conflict with regular exit codes returned by
  77     <function>sd_event_loop()</function>, if these exit codes shall be
  78     distinguishable.</para>
  79
  80     <para>Note that for most event source types passing the callback pointer as <constant>NULL</constant> in
  81     the respective constructor call (i.e. in
  82     <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  83     <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  84     …) has the effect of <function>sd_event_exit()</function> being invoked once the event source triggers,
  85     with the specified userdata pointer cast to an integer as the exit code parameter. This is useful to
  86     automatically terminate an event loop after some condition, such as a time-out or reception of
  87     <constant>SIGTERM</constant> or similar. See the documentation for the respective constructor call for
  88     details.</para>
  89   </refsect1>
  90
  91   <refsect1>
  92     <title>Return Value</title>
  93
  94     <para>On success, <function>sd_event_exit()</function> and <function>sd_event_get_exit_code()</function>
  95     return 0 or a positive integer. On failure, they return a negative errno-style error code.</para>
  96
  97     <refsect2>
  98       <title>Errors</title>
  99
 100       <para>Returned errors may indicate the following problems:</para>
 101
 102       <variablelist>
 103
 104         <varlistentry>
 105           <term><constant>-EINVAL</constant></term>
 106
 107           <listitem><para>The event loop object or error code pointer are invalid.</para></listitem>
 108
 109         </varlistentry>
 110
 111         <varlistentry>
 112           <term><constant>-ECHILD</constant></term>
 113
 114           <listitem><para>The event loop was created in a different process, library or module instance.</para></listitem>
 115         </varlistentry>
 116
 117         <varlistentry>
 118           <term><constant>-ESTALE</constant></term>
 119
 120           <listitem><para>The event loop has exited already and all exit handlers are already processed.
 121           </para></listitem>
 122         </varlistentry>
 123
 124         <varlistentry>
 125           <term><constant>-ENODATA</constant></term>
 126
 127           <listitem><para>Returned by <function>sd_event_get_exit_code()</function> in case the event loop has not
 128           been requested to exit yet.</para></listitem>
 129         </varlistentry>
 130
 131       </variablelist>
 132     </refsect2>
 133   </refsect1>
 134
 135   <xi:include href="libsystemd-pkgconfig.xml" />
 136
 137   <refsect1>
 138     <title>History</title>
 139     <para><function>sd_event_exit()</function> and
 140     <function>sd_event_get_exit_code()</function> were added in version 229.</para>
 141   </refsect1>
 142
 143   <refsect1>
 144     <title>See Also</title>
 145
 146     <para><simplelist type="inline">
 147       <member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
 148       <member><citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
 149       <member><citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
 150       <member><citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
 151       <member><citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
 152       <member><citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
 153       <member><citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
 154       <member><citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
 155       <member><citerefentry><refentrytitle>sd_event_add_inotify</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
 156     </simplelist></para>
 157   </refsect1>
 158
 159 </refentry>