sd-event: define a new PREPARING state

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

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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">

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

  <refentryinfo>
    <title>sd_event_get_fd</title>
    <productname>systemd</productname>

    <authorgroup>
      <author>
        <contrib>More text</contrib>
        <firstname>Zbigniew</firstname>
        <surname>Jędrzejewski-Szmek</surname>
        <email>zbyszek@in.waw.pl</email>
      </author>
    </authorgroup>
  </refentryinfo>

  <refmeta>
    <refentrytitle>sd_event_get_fd</refentrytitle>
    <manvolnum>3</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>sd_event_get_fd</refname>

    <refpurpose>Obtain a file descriptor to poll for event loop events</refpurpose>
  </refnamediv>

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

      <funcprototype>
        <funcdef>int <function>sd_event_get_fd</function></funcdef>
        <paramdef>sd_bus *<parameter>event</parameter></paramdef>
      </funcprototype>

    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para><function>sd_event_get_fd()</function> returns the file
    descriptor that the event loop object returned by the
    <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    function uses to wait for events. This file descriptor can be
    polled for events. This makes it possible to embed the
    <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    event loop inside of another event loop.</para>
  </refsect1>

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

    <para>On success, <function>sd_event_get_fd()</function> returns a
    non-negative integer. On failure, it returns a negative
    errno-style error code.</para>
  </refsect1>

  <refsect1>
    <title>Errors</title>

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

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

        <listitem><para><parameter>event</parameter> is not a valid
        pointer to an <structname>sd_event</structname> structure.
        </para></listitem>
      </varlistentry>

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

        <listitem><para>The event loop has been created in a different process.</para></listitem>

      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Examples</title>

    <example>
      <title>Integration in glib event loop</title>

      <programlisting><xi:include href="glib-event-glue.c" parse="text" /></programlisting>
    </example>
  </refsect1>

  <refsect1>
    <title>Notes</title>

    <para><function>sd_event_get_fd()</function> is available as a
    shared library, which can be compiled and linked to with the
    <constant>libsystemd</constant> <citerefentry
    project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
    file.</para>
  </refsect1>

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

    <para>
      <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_event_ref</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    </para>
  </refsect1>

</refentry>