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
  83     non-negative integer. On failure, they return a negative
  84     errno-style error code.</para>
  85   </refsect1>
  86
  87   <refsect1>
  88     <title>Errors</title>
  89
  90     <para>Returned errors may indicate the following problems:</para>
  91
  92     <variablelist>
  93       <varlistentry>
  94         <term><constant>-EINVAL</constant></term>
  95
  96         <listitem><para><parameter>source</parameter> is not a valid
  97         pointer to an <structname>sd_event_source</structname>
  98         object or the <parameter>description</parameter> argument for
  99         <function>sd_event_source_get_description()</function> is
 100         <constant>NULL</constant>.</para></listitem>
 101       </varlistentry>
 102
 103       <varlistentry>
 104         <term><constant>-ENOMEM</constant></term>
 105
 106         <listitem><para>Not enough memory to copy the
 107         name.</para></listitem>
 108       </varlistentry>
 109
 110       <varlistentry>
 111         <term><constant>-ECHILD</constant></term>
 112
 113         <listitem><para>The event loop has been created in a different process.</para></listitem>
 114
 115       </varlistentry>
 116
 117       <varlistentry>
 118         <term><constant>-ENXIO</constant></term>
 119
 120         <listitem><para>No name was set for the event
 121         source.</para></listitem>
 122       </varlistentry>
 123
 124     </variablelist>
 125   </refsect1>
 126
 127   <xi:include href="libsystemd-pkgconfig.xml" />
 128
 129   <refsect1>
 130     <title>See Also</title>
 131
 132     <para>
 133       <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 134       <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 135       <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 136       <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 137       <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 138       <citerefentry><refentrytitle>sd_event_add_inotify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 139       <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 140       <citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 141     </para>
 142   </refsect1>
 143
 144 </refentry>