man/sd_event_source_set_userdata.xml

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  10   Copyright 2015 Lennart Poettering
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  25
  26 <refentry id="sd_event_source_set_userdata" xmlns:xi="http://www.w3.org/2001/XInclude">
  27
  28   <refentryinfo>
  29     <title>sd_event_source_set_userdata</title>
  30     <productname>systemd</productname>
  31
  32     <authorgroup>
  33       <author>
  34         <contrib>Developer</contrib>
  35         <firstname>Lennart</firstname>
  36         <surname>Poettering</surname>
  37         <email>lennart@poettering.net</email>
  38       </author>
  39     </authorgroup>
  40   </refentryinfo>
  41
  42   <refmeta>
  43     <refentrytitle>sd_event_source_set_userdata</refentrytitle>
  44     <manvolnum>3</manvolnum>
  45   </refmeta>
  46
  47   <refnamediv>
  48     <refname>sd_event_source_set_userdata</refname>
  49     <refname>sd_event_source_get_userdata</refname>
  50
  51     <refpurpose>Set or retrieve user data pointer of event sources</refpurpose>
  52   </refnamediv>
  53
  54   <refsynopsisdiv>
  55     <funcsynopsis>
  56       <funcsynopsisinfo>#include &lt;systemd/sd-event.h&gt;</funcsynopsisinfo>
  57
  58       <funcprototype>
  59         <funcdef>void* <function>sd_event_source_set_userdata</function></funcdef>
  60         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  61         <paramdef>void *<parameter>userdata</parameter></paramdef>
  62       </funcprototype>
  63
  64       <funcprototype>
  65         <funcdef>void* <function>sd_event_source_get_userdata</function></funcdef>
  66         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
  67       </funcprototype>
  68
  69     </funcsynopsis>
  70   </refsynopsisdiv>
  71
  72   <refsect1>
  73     <title>Description</title>
  74
  75     <para><function>sd_event_source_set_userdata()</function> may be
  76     used to set an arbitrary user data pointer for the event source
  77     object specified as <parameter>source</parameter>. The user data
  78     pointer is usually specified when creating an event source object
  79     with calls such as
  80     <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  81     or
  82     <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  83     and may be updated with this call. The user data pointer is also
  84     passed to all handler callback functions associated with the event
  85     source. The <parameter>userdata</parameter> parameter specifies
  86     the new user data pointer to set, the function returns the
  87     previous user data pointer. Note that <constant>NULL</constant> is
  88     a valid user data pointer.</para>
  89
  90     <para><function>sd_event_source_get_userdata()</function> may be
  91     used to query the current user data pointer assigned to the event
  92     source object <parameter>source</parameter>.</para>
  93   </refsect1>
  94
  95   <refsect1>
  96     <title>Return Value</title>
  97
  98     <para>On success,
  99     <function>sd_event_source_set_userdata()</function> and
 100     <function>sd_event_source_get_userdata()</function> return the
 101     previously set user data pointer. On failure, they return
 102     NULL.</para>
 103   </refsect1>
 104
 105   <xi:include href="libsystemd-pkgconfig.xml" />
 106
 107   <refsect1>
 108     <title>See Also</title>
 109
 110     <para>
 111       <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 112       <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 113       <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 114       <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 115       <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 116       <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 117       <citerefentry><refentrytitle>sd_event_source_set_description</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 118     </para>
 119   </refsect1>
 120
 121 </refentry>