man/sd_event_source_set_description.xml

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   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4
   5 <!--
   6   SPDX-License-Identifier: LGPL-2.1+
   7 -->
   8
   9 <refentry id="sd_event_source_set_description" xmlns:xi="http://www.w3.org/2001/XInclude">
  10
  11   <refentryinfo>
  12     <title>sd_event_source_set_description</title>
  13     <productname>systemd</productname>
  14   </refentryinfo>
  15
  16   <refmeta>
  17     <refentrytitle>sd_event_source_set_description</refentrytitle>
  18     <manvolnum>3</manvolnum>
  19   </refmeta>
  20
  21   <refnamediv>
  22     <refname>sd_event_source_set_description</refname>
  23     <refname>sd_event_source_get_description</refname>
  24
  25     <refpurpose>Set or retrieve descriptive names of event sources</refpurpose>
  26   </refnamediv>
  27
  28   <refsynopsisdiv>
  29     <funcsynopsis>
  30       <funcsynopsisinfo>#include &lt;systemd/sd-event.h&gt;</funcsynopsisinfo>
  31
  32       <funcprototype>
  33         <funcdef>int <function>sd_event_source_set_description</function></funcdef>
  34         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  35         <paramdef>const char *<parameter>description</parameter></paramdef>
  36       </funcprototype>
  37
  38       <funcprototype>
  39         <funcdef>int <function>sd_event_source_get_description</function></funcdef>
  40         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  41         <paramdef>const char **<parameter>description</parameter></paramdef>
  42       </funcprototype>
  43
  44     </funcsynopsis>
  45   </refsynopsisdiv>
  46
  47   <refsect1>
  48     <title>Description</title>
  49
  50     <para><function>sd_event_source_set_description()</function> may
  51     be used to set an arbitrary descriptive name for the event source
  52     object specified as <parameter>source</parameter>. This name will
  53     be used in debugging messages generated by
  54     <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  55     for this event source, and may be queried using
  56     <function>sd_event_source_get_description()</function> for
  57     debugging purposes. The <parameter>description</parameter> parameter shall
  58     point to a <constant>NUL</constant>-terminated string or be
  59     <constant>NULL</constant>. In the latter case, the descriptive
  60     name will be unset. The string is copied internally, hence the
  61     <parameter>description</parameter> argument is not referenced
  62     after the function returns.</para>
  63
  64     <para><function>sd_event_source_get_description()</function> may
  65     be used to query the current descriptive name assigned to the
  66     event source object <parameter>source</parameter>. It returns a
  67     pointer to the current name in <parameter>description</parameter>,
  68     stored in memory internal to the event source. The memory is
  69     invalidated when the event source is destroyed or the descriptive
  70     name is changed.</para>
  71
  72     <para>Event source objects generally have no description set when
  73     they are created, except for UNIX signal event sources created
  74     with
  75     <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  76     whose descriptive name is initialized to the signal's C constant
  77     name (e.g. <literal>SIGINT</literal> or
  78     <literal>SIGTERM</literal>).</para>
  79   </refsect1>
  80
  81   <refsect1>
  82     <title>Return Value</title>
  83
  84     <para>On success, <function>sd_event_source_set_description()</function> and
  85     <function>sd_event_source_get_description()</function> return a
  86     non-negative integer. On failure, they return a negative
  87     errno-style error code.</para>
  88   </refsect1>
  89
  90   <refsect1>
  91     <title>Errors</title>
  92
  93     <para>Returned errors may indicate the following problems:</para>
  94
  95     <variablelist>
  96       <varlistentry>
  97         <term><constant>-EINVAL</constant></term>
  98
  99         <listitem><para><parameter>source</parameter> is not a valid
 100         pointer to an <structname>sd_event_source</structname>
 101         object or the <parameter>description</parameter> argument for
 102         <function>sd_event_source_get_description()</function> is
 103         <constant>NULL</constant>.</para></listitem>
 104       </varlistentry>
 105
 106       <varlistentry>
 107         <term><constant>-ENOMEM</constant></term>
 108
 109         <listitem><para>Not enough memory to copy the
 110         name.</para></listitem>
 111       </varlistentry>
 112
 113       <varlistentry>
 114         <term><constant>-ECHILD</constant></term>
 115
 116         <listitem><para>The event loop has been created in a different process.</para></listitem>
 117
 118       </varlistentry>
 119
 120       <varlistentry>
 121         <term><constant>-ENXIO</constant></term>
 122
 123         <listitem><para>No name was set for the event
 124         source.</para></listitem>
 125       </varlistentry>
 126
 127     </variablelist>
 128   </refsect1>
 129
 130   <xi:include href="libsystemd-pkgconfig.xml" />
 131
 132   <refsect1>
 133     <title>See Also</title>
 134
 135     <para>
 136       <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 137       <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 138       <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 139       <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 140       <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 141       <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 142       <citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 143     </para>
 144   </refsect1>
 145
 146 </refentry>