man/sd_event_source_set_userdata.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-or-later -->
   5
   6 <refentry id="sd_event_source_set_userdata" xmlns:xi="http://www.w3.org/2001/XInclude">
   7
   8   <refentryinfo>
   9     <title>sd_event_source_set_userdata</title>
  10     <productname>systemd</productname>
  11   </refentryinfo>
  12
  13   <refmeta>
  14     <refentrytitle>sd_event_source_set_userdata</refentrytitle>
  15     <manvolnum>3</manvolnum>
  16   </refmeta>
  17
  18   <refnamediv>
  19     <refname>sd_event_source_set_userdata</refname>
  20     <refname>sd_event_source_get_userdata</refname>
  21
  22     <refpurpose>Set or retrieve user data pointer 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>void* <function>sd_event_source_set_userdata</function></funcdef>
  31         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  32         <paramdef>void *<parameter>userdata</parameter></paramdef>
  33       </funcprototype>
  34
  35       <funcprototype>
  36         <funcdef>void* <function>sd_event_source_get_userdata</function></funcdef>
  37         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  38       </funcprototype>
  39
  40     </funcsynopsis>
  41   </refsynopsisdiv>
  42
  43   <refsect1>
  44     <title>Description</title>
  45
  46     <para><function>sd_event_source_set_userdata()</function> may be
  47     used to set an arbitrary user data pointer for the event source
  48     object specified as <parameter>source</parameter>. The user data
  49     pointer is usually specified when creating an event source object
  50     with calls such as
  51     <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  52     or
  53     <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  54     and may be updated with this call. The user data pointer is also
  55     passed to all handler callback functions associated with the event
  56     source. The <parameter>userdata</parameter> parameter specifies
  57     the new user data pointer to set, the function returns the
  58     previous user data pointer. Note that <constant>NULL</constant> is
  59     a valid user data pointer.</para>
  60
  61     <para><function>sd_event_source_get_userdata()</function> may be
  62     used to query the current user data pointer assigned to the event
  63     source object <parameter>source</parameter>.</para>
  64   </refsect1>
  65
  66   <refsect1>
  67     <title>Return Value</title>
  68
  69     <para>On success,
  70     <function>sd_event_source_set_userdata()</function> and
  71     <function>sd_event_source_get_userdata()</function> return the
  72     previously set user data pointer. On failure, they return
  73     <constant>NULL</constant>.</para>
  74   </refsect1>
  75
  76   <xi:include href="libsystemd-pkgconfig.xml" />
  77
  78   <refsect1>
  79     <title>History</title>
  80     <para><function>sd_event_source_set_userdata()</function> and
  81     <function>sd_event_source_get_userdata()</function> were added in version 229.</para>
  82   </refsect1>
  83
  84   <refsect1>
  85     <title>See Also</title>
  86
  87     <para>
  88       <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  89       <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  90       <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  91       <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  92       <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  93       <citerefentry><refentrytitle>sd_event_add_inotify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  94       <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  95       <citerefentry><refentrytitle>sd_event_source_set_description</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  96     </para>
  97   </refsect1>
  98
  99 </refentry>