Merge pull request #17732 from yuwata/core-use-synthetic_errno

[thirdparty/systemd.git] / man / sd_event_exit.xml

<?xml version='1.0'?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->

<refentry id="sd_event_exit" xmlns:xi="http://www.w3.org/2001/XInclude">

  <refentryinfo>
    <title>sd_event_exit</title>
    <productname>systemd</productname>
  </refentryinfo>

  <refmeta>
    <refentrytitle>sd_event_exit</refentrytitle>
    <manvolnum>3</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>sd_event_exit</refname>
    <refname>sd_event_get_exit_code</refname>

    <refpurpose>Ask the event loop to exit</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <funcsynopsis>
      <funcsynopsisinfo>#include &lt;systemd/sd-event.h&gt;</funcsynopsisinfo>

      <funcprototype>
        <funcdef>int <function>sd_event_exit</function></funcdef>
        <paramdef>sd_event *<parameter>event</parameter></paramdef>
        <paramdef>int <parameter>code</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_event_get_exit_code</function></funcdef>
        <paramdef>sd_event *<parameter>event</parameter></paramdef>
        <paramdef>int *<parameter>code</parameter></paramdef>
      </funcprototype>

    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para><function>sd_event_exit()</function> requests the event loop
    specified in the <parameter>event</parameter> event loop object to
    exit. The <parameter>code</parameter> parameter may be any integer
    value and is returned as-is by
    <citerefentry><refentrytitle>sd_event_loop</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    after the last event loop iteration. It may also be queried
    using <function>sd_event_get_exit_code()</function>, see
    below. </para>

    <para>When exiting is requested the event loop will stop listening
    for and dispatching regular event sources. Instead it will proceed
    with executing only event sources registered with
    <citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    in the order defined by their priority. After all exit event
    sources have been dispatched the event loop is terminated.</para>

    <para>If <function>sd_event_exit()</function> is invoked a second
    time while the event loop is still processing exit event sources,
    the exit code stored in the event loop object is updated, but
    otherwise no further operation is executed.</para>

    <para><function>sd_event_get_exit_code()</function> may be used to
    query the exit code passed into
    <function>sd_event_exit()</function> earlier.</para>

    <para>While the full positive and negative integer ranges may be used
    for the exit code, care should be taken not pick exit codes that
    conflict with regular exit codes returned by
    <function>sd_event_loop()</function>, if these exit codes shall be
    distinguishable.</para>

    <para>Note that for most event source types passing the callback pointer as <constant>NULL</constant> in
    the respective constructor call (i.e. in
    <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
    <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
    …) has the effect of <function>sd_event_exit()</function> being invoked once the event source triggers,
    with the specified userdata pointer cast to an integer as the exit code parameter. This is useful to
    automatically terminate an event loop after some condition, such as a time-out or reception of
    <constant>SIGTERM</constant> or similar. See the documentation for the respective constructor call for
    details.</para>
  </refsect1>

  <refsect1>
    <title>Return Value</title>

    <para>On success, <function>sd_event_exit()</function> and <function>sd_event_get_exit_code()</function>
    return 0 or a positive integer. On failure, they return a negative errno-style error code.</para>

    <refsect2>
      <title>Errors</title>

      <para>Returned errors may indicate the following problems:</para>

      <variablelist>

        <varlistentry>
          <term><constant>-EINVAL</constant></term>

          <listitem><para>The event loop object or error code pointer are invalid.</para></listitem>

        </varlistentry>

        <varlistentry>
          <term><constant>-ECHILD</constant></term>

          <listitem><para>The event loop was created in a different process.</para></listitem>
        </varlistentry>

        <varlistentry>
          <term><constant>-ESTALE</constant></term>

          <listitem><para>The event loop has exited already and all exit handlers are already processed.
          </para></listitem>
        </varlistentry>

        <varlistentry>
          <term><constant>-ENODATA</constant></term>

          <listitem><para>The event loop has not been requested to exit yet.</para></listitem>
        </varlistentry>

      </variablelist>
    </refsect2>
  </refsect1>

  <xi:include href="libsystemd-pkgconfig.xml" />

  <refsect1>
    <title>See Also</title>

    <para>
      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_event_add_inotify</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    </para>
  </refsect1>

</refentry>