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

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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">

<!--
  SPDX-License-Identifier: LGPL-2.1+

  Copyright © 2014 Zbigniew Jędrzejewski-Szmek
-->

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

  <refentryinfo>
    <title>sd_event_source_set_description</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_source_set_description</refentrytitle>
    <manvolnum>3</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>sd_event_source_set_description</refname>
    <refname>sd_event_source_get_description</refname>

    <refpurpose>Set or retrieve descriptive names of event sources</refpurpose>
  </refnamediv>

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

      <funcprototype>
        <funcdef>int <function>sd_event_source_set_description</function></funcdef>
        <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
        <paramdef>const char *<parameter>description</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_event_source_get_description</function></funcdef>
        <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
        <paramdef>const char **<parameter>description</parameter></paramdef>
      </funcprototype>

    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para><function>sd_event_source_set_description()</function> may
    be used to set an arbitrary descriptive name for the event source
    object specified as <parameter>source</parameter>. This name will
    be used in debugging messages generated by
    <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    for this event source, and may be queried using
    <function>sd_event_source_get_description()</function> for
    debugging purposes. The <parameter>description</parameter> parameter shall
    point to a <constant>NUL</constant>-terminated string or be
    <constant>NULL</constant>. In the latter case, the descriptive
    name will be unset. The string is copied internally, hence the
    <parameter>description</parameter> argument is not referenced
    after the function returns.</para>

    <para><function>sd_event_source_get_description()</function> may
    be used to query the current descriptive name assigned to the
    event source object <parameter>source</parameter>. It returns a
    pointer to the current name in <parameter>description</parameter>,
    stored in memory internal to the event source. The memory is
    invalidated when the event source is destroyed or the descriptive
    name is changed.</para>

    <para>Event source objects generally have no description set when
    they are created, except for UNIX signal event sources created
    with
    <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
    whose descriptive name is initialized to the signal's C constant
    name (e.g. <literal>SIGINT</literal> or
    <literal>SIGTERM</literal>).</para>
  </refsect1>

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

    <para>On success, <function>sd_event_source_set_description()</function> and
    <function>sd_event_source_get_description()</function> return a
    non-negative integer. On failure, they return 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>source</parameter> is not a valid
        pointer to an <structname>sd_event_source</structname>
        object or the <parameter>description</parameter> argument for
        <function>sd_event_source_get_description()</function> is
        <constant>NULL</constant>.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><constant>-ENOMEM</constant></term>

        <listitem><para>Not enough memory to copy the
        name.</para></listitem>
      </varlistentry>

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

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

      </varlistentry>

      <varlistentry>
        <term><constant>-ENXIO</constant></term>

        <listitem><para>No name was set for the event
        source.</para></listitem>
      </varlistentry>

    </variablelist>
  </refsect1>

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

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

    <para>
      <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    </para>
  </refsect1>

</refentry>