man/sd_event_source_set_userdata.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">
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   5 <!--
   6   SPDX-License-Identifier: LGPL-2.1+
   7 -->
   8
   9 <refentry id="sd_event_source_set_userdata" xmlns:xi="http://www.w3.org/2001/XInclude">
  10
  11   <refentryinfo>
  12     <title>sd_event_source_set_userdata</title>
  13     <productname>systemd</productname>
  14
  15     <authorgroup>
  16       <author>
  17         <contrib>Developer</contrib>
  18         <firstname>Lennart</firstname>
  19         <surname>Poettering</surname>
  20         <email>lennart@poettering.net</email>
  21       </author>
  22     </authorgroup>
  23   </refentryinfo>
  24
  25   <refmeta>
  26     <refentrytitle>sd_event_source_set_userdata</refentrytitle>
  27     <manvolnum>3</manvolnum>
  28   </refmeta>
  29
  30   <refnamediv>
  31     <refname>sd_event_source_set_userdata</refname>
  32     <refname>sd_event_source_get_userdata</refname>
  33
  34     <refpurpose>Set or retrieve user data pointer of event sources</refpurpose>
  35   </refnamediv>
  36
  37   <refsynopsisdiv>
  38     <funcsynopsis>
  39       <funcsynopsisinfo>#include &lt;systemd/sd-event.h&gt;</funcsynopsisinfo>
  40
  41       <funcprototype>
  42         <funcdef>void* <function>sd_event_source_set_userdata</function></funcdef>
  43         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  44         <paramdef>void *<parameter>userdata</parameter></paramdef>
  45       </funcprototype>
  46
  47       <funcprototype>
  48         <funcdef>void* <function>sd_event_source_get_userdata</function></funcdef>
  49         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  50       </funcprototype>
  51
  52     </funcsynopsis>
  53   </refsynopsisdiv>
  54
  55   <refsect1>
  56     <title>Description</title>
  57
  58     <para><function>sd_event_source_set_userdata()</function> may be
  59     used to set an arbitrary user data pointer for the event source
  60     object specified as <parameter>source</parameter>. The user data
  61     pointer is usually specified when creating an event source object
  62     with calls such as
  63     <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  64     or
  65     <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  66     and may be updated with this call. The user data pointer is also
  67     passed to all handler callback functions associated with the event
  68     source. The <parameter>userdata</parameter> parameter specifies
  69     the new user data pointer to set, the function returns the
  70     previous user data pointer. Note that <constant>NULL</constant> is
  71     a valid user data pointer.</para>
  72
  73     <para><function>sd_event_source_get_userdata()</function> may be
  74     used to query the current user data pointer assigned to the event
  75     source object <parameter>source</parameter>.</para>
  76   </refsect1>
  77
  78   <refsect1>
  79     <title>Return Value</title>
  80
  81     <para>On success,
  82     <function>sd_event_source_set_userdata()</function> and
  83     <function>sd_event_source_get_userdata()</function> return the
  84     previously set user data pointer. On failure, they return
  85     NULL.</para>
  86   </refsect1>
  87
  88   <xi:include href="libsystemd-pkgconfig.xml" />
  89
  90   <refsect1>
  91     <title>See Also</title>
  92
  93     <para>
  94       <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  95       <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  96       <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  97       <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  98       <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  99       <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 100       <citerefentry><refentrytitle>sd_event_source_set_description</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 101     </para>
 102   </refsect1>
 103
 104 </refentry>