man/sd_event_source_set_userdata.xml

   1 <?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
   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   Copyright 2015 Lennart Poettering
   9 -->
  10
  11 <refentry id="sd_event_source_set_userdata" xmlns:xi="http://www.w3.org/2001/XInclude">
  12
  13   <refentryinfo>
  14     <title>sd_event_source_set_userdata</title>
  15     <productname>systemd</productname>
  16
  17     <authorgroup>
  18       <author>
  19         <contrib>Developer</contrib>
  20         <firstname>Lennart</firstname>
  21         <surname>Poettering</surname>
  22         <email>lennart@poettering.net</email>
  23       </author>
  24     </authorgroup>
  25   </refentryinfo>
  26
  27   <refmeta>
  28     <refentrytitle>sd_event_source_set_userdata</refentrytitle>
  29     <manvolnum>3</manvolnum>
  30   </refmeta>
  31
  32   <refnamediv>
  33     <refname>sd_event_source_set_userdata</refname>
  34     <refname>sd_event_source_get_userdata</refname>
  35
  36     <refpurpose>Set or retrieve user data pointer of event sources</refpurpose>
  37   </refnamediv>
  38
  39   <refsynopsisdiv>
  40     <funcsynopsis>
  41       <funcsynopsisinfo>#include &lt;systemd/sd-event.h&gt;</funcsynopsisinfo>
  42
  43       <funcprototype>
  44         <funcdef>void* <function>sd_event_source_set_userdata</function></funcdef>
  45         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  46         <paramdef>void *<parameter>userdata</parameter></paramdef>
  47       </funcprototype>
  48
  49       <funcprototype>
  50         <funcdef>void* <function>sd_event_source_get_userdata</function></funcdef>
  51         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  52       </funcprototype>
  53
  54     </funcsynopsis>
  55   </refsynopsisdiv>
  56
  57   <refsect1>
  58     <title>Description</title>
  59
  60     <para><function>sd_event_source_set_userdata()</function> may be
  61     used to set an arbitrary user data pointer for the event source
  62     object specified as <parameter>source</parameter>. The user data
  63     pointer is usually specified when creating an event source object
  64     with calls such as
  65     <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  66     or
  67     <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  68     and may be updated with this call. The user data pointer is also
  69     passed to all handler callback functions associated with the event
  70     source. The <parameter>userdata</parameter> parameter specifies
  71     the new user data pointer to set, the function returns the
  72     previous user data pointer. Note that <constant>NULL</constant> is
  73     a valid user data pointer.</para>
  74
  75     <para><function>sd_event_source_get_userdata()</function> may be
  76     used to query the current user data pointer assigned to the event
  77     source object <parameter>source</parameter>.</para>
  78   </refsect1>
  79
  80   <refsect1>
  81     <title>Return Value</title>
  82
  83     <para>On success,
  84     <function>sd_event_source_set_userdata()</function> and
  85     <function>sd_event_source_get_userdata()</function> return the
  86     previously set user data pointer. On failure, they return
  87     NULL.</para>
  88   </refsect1>
  89
  90   <xi:include href="libsystemd-pkgconfig.xml" />
  91
  92   <refsect1>
  93     <title>See Also</title>
  94
  95     <para>
  96       <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  97       <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  98       <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  99       <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 100       <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 101       <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 102       <citerefentry><refentrytitle>sd_event_source_set_description</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 103     </para>
 104   </refsect1>
 105
 106 </refentry>