man/sd_event_source_set_userdata.xml

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   4
   5 <!--
   6   SPDX-License-Identifier: LGPL-2.1+
   7
   8   This file is part of systemd.
   9
  10   Copyright 2015 Lennart Poettering
  11 -->
  12
  13 <refentry id="sd_event_source_set_userdata" xmlns:xi="http://www.w3.org/2001/XInclude">
  14
  15   <refentryinfo>
  16     <title>sd_event_source_set_userdata</title>
  17     <productname>systemd</productname>
  18
  19     <authorgroup>
  20       <author>
  21         <contrib>Developer</contrib>
  22         <firstname>Lennart</firstname>
  23         <surname>Poettering</surname>
  24         <email>lennart@poettering.net</email>
  25       </author>
  26     </authorgroup>
  27   </refentryinfo>
  28
  29   <refmeta>
  30     <refentrytitle>sd_event_source_set_userdata</refentrytitle>
  31     <manvolnum>3</manvolnum>
  32   </refmeta>
  33
  34   <refnamediv>
  35     <refname>sd_event_source_set_userdata</refname>
  36     <refname>sd_event_source_get_userdata</refname>
  37
  38     <refpurpose>Set or retrieve user data pointer of event sources</refpurpose>
  39   </refnamediv>
  40
  41   <refsynopsisdiv>
  42     <funcsynopsis>
  43       <funcsynopsisinfo>#include &lt;systemd/sd-event.h&gt;</funcsynopsisinfo>
  44
  45       <funcprototype>
  46         <funcdef>void* <function>sd_event_source_set_userdata</function></funcdef>
  47         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  48         <paramdef>void *<parameter>userdata</parameter></paramdef>
  49       </funcprototype>
  50
  51       <funcprototype>
  52         <funcdef>void* <function>sd_event_source_get_userdata</function></funcdef>
  53         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  54       </funcprototype>
  55
  56     </funcsynopsis>
  57   </refsynopsisdiv>
  58
  59   <refsect1>
  60     <title>Description</title>
  61
  62     <para><function>sd_event_source_set_userdata()</function> may be
  63     used to set an arbitrary user data pointer for the event source
  64     object specified as <parameter>source</parameter>. The user data
  65     pointer is usually specified when creating an event source object
  66     with calls such as
  67     <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  68     or
  69     <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  70     and may be updated with this call. The user data pointer is also
  71     passed to all handler callback functions associated with the event
  72     source. The <parameter>userdata</parameter> parameter specifies
  73     the new user data pointer to set, the function returns the
  74     previous user data pointer. Note that <constant>NULL</constant> is
  75     a valid user data pointer.</para>
  76
  77     <para><function>sd_event_source_get_userdata()</function> may be
  78     used to query the current user data pointer assigned to the event
  79     source object <parameter>source</parameter>.</para>
  80   </refsect1>
  81
  82   <refsect1>
  83     <title>Return Value</title>
  84
  85     <para>On success,
  86     <function>sd_event_source_set_userdata()</function> and
  87     <function>sd_event_source_get_userdata()</function> return the
  88     previously set user data pointer. On failure, they return
  89     NULL.</para>
  90   </refsect1>
  91
  92   <xi:include href="libsystemd-pkgconfig.xml" />
  93
  94   <refsect1>
  95     <title>See Also</title>
  96
  97     <para>
  98       <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  99       <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 100       <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 101       <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 102       <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 103       <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 104       <citerefentry><refentrytitle>sd_event_source_set_description</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 105     </para>
 106   </refsect1>
 107
 108 </refentry>