man/sd_event_source_set_description.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/4.2/docbookx.dtd">
   4 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
   5
   6 <refentry id="sd_event_source_set_description" xmlns:xi="http://www.w3.org/2001/XInclude">
   7
   8   <refentryinfo>
   9     <title>sd_event_source_set_description</title>
  10     <productname>systemd</productname>
  11   </refentryinfo>
  12
  13   <refmeta>
  14     <refentrytitle>sd_event_source_set_description</refentrytitle>
  15     <manvolnum>3</manvolnum>
  16   </refmeta>
  17
  18   <refnamediv>
  19     <refname>sd_event_source_set_description</refname>
  20     <refname>sd_event_source_get_description</refname>
  21
  22     <refpurpose>Set or retrieve descriptive names of event sources</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_source_set_description</function></funcdef>
  31         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  32         <paramdef>const char *<parameter>description</parameter></paramdef>
  33       </funcprototype>
  34
  35       <funcprototype>
  36         <funcdef>int <function>sd_event_source_get_description</function></funcdef>
  37         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  38         <paramdef>const char **<parameter>description</parameter></paramdef>
  39       </funcprototype>
  40
  41     </funcsynopsis>
  42   </refsynopsisdiv>
  43
  44   <refsect1>
  45     <title>Description</title>
  46
  47     <para><function>sd_event_source_set_description()</function> may
  48     be used to set an arbitrary descriptive name for the event source
  49     object specified as <parameter>source</parameter>. This name will
  50     be used in debugging messages generated by
  51     <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  52     for this event source, and may be queried using
  53     <function>sd_event_source_get_description()</function> for
  54     debugging purposes. The <parameter>description</parameter> parameter shall
  55     point to a <constant>NUL</constant>-terminated string or be
  56     <constant>NULL</constant>. In the latter case, the descriptive
  57     name will be unset. The string is copied internally, hence the
  58     <parameter>description</parameter> argument is not referenced
  59     after the function returns.</para>
  60
  61     <para><function>sd_event_source_get_description()</function> may
  62     be used to query the current descriptive name assigned to the
  63     event source object <parameter>source</parameter>. It returns a
  64     pointer to the current name in <parameter>description</parameter>,
  65     stored in memory internal to the event source. The memory is
  66     invalidated when the event source is destroyed or the descriptive
  67     name is changed.</para>
  68
  69     <para>Event source objects generally have no description set when
  70     they are created, except for UNIX signal event sources created
  71     with
  72     <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  73     whose descriptive name is initialized to the signal's C constant
  74     name (e.g. <literal>SIGINT</literal> or
  75     <literal>SIGTERM</literal>).</para>
  76   </refsect1>
  77
  78   <refsect1>
  79     <title>Return Value</title>
  80
  81     <para>On success, <function>sd_event_source_set_description()</function> and
  82     <function>sd_event_source_get_description()</function> return a non-negative integer. On failure, they
  83     return a negative errno-style error code.</para>
  84
  85     <refsect2>
  86       <title>Errors</title>
  87
  88       <para>Returned errors may indicate the following problems:</para>
  89
  90       <variablelist>
  91         <varlistentry>
  92           <term><constant>-EINVAL</constant></term>
  93
  94           <listitem><para><parameter>source</parameter> is not a valid pointer to an
  95           <structname>sd_event_source</structname> object or the <parameter>description</parameter> argument
  96           for <function>sd_event_source_get_description()</function> is <constant>NULL</constant>.
  97           </para></listitem>
  98         </varlistentry>
  99
 100         <varlistentry>
 101           <term><constant>-ENOMEM</constant></term>
 102
 103           <listitem><para>Not enough memory to copy the name.</para></listitem>
 104         </varlistentry>
 105
 106         <varlistentry>
 107           <term><constant>-ECHILD</constant></term>
 108
 109           <listitem><para>The event loop has been created in a different process.</para></listitem>
 110
 111         </varlistentry>
 112
 113         <varlistentry>
 114           <term><constant>-ENXIO</constant></term>
 115
 116           <listitem><para>No name was set for the event source.</para></listitem>
 117         </varlistentry>
 118
 119       </variablelist>
 120     </refsect2>
 121   </refsect1>
 122
 123   <xi:include href="libsystemd-pkgconfig.xml" />
 124
 125   <refsect1>
 126     <title>See Also</title>
 127
 128     <para>
 129       <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 130       <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 131       <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 132       <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 133       <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 134       <citerefentry><refentrytitle>sd_event_add_inotify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 135       <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 136       <citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 137     </para>
 138   </refsect1>
 139
 140 </refentry>