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<?xml version='1.0'?>
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< !DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!-- SPDX - License - Identifier: LGPL - 2.1 - or - later -->
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<refentry id= "sd_event_source_set_userdata" xmlns:xi= "http://www.w3.org/2001/XInclude" >
<refentryinfo >
<title > sd_event_source_set_userdata</title>
<productname > systemd</productname>
</refentryinfo>
<refmeta >
<refentrytitle > sd_event_source_set_userdata</refentrytitle>
<manvolnum > 3</manvolnum>
</refmeta>
<refnamediv >
<refname > sd_event_source_set_userdata</refname>
<refname > sd_event_source_get_userdata</refname>
<refpurpose > Set or retrieve user data pointer of event sources</refpurpose>
</refnamediv>
<refsynopsisdiv >
<funcsynopsis >
<funcsynopsisinfo > #include < systemd/sd-event.h> </funcsynopsisinfo>
<funcprototype >
<funcdef > void* <function > sd_event_source_set_userdata</function> </funcdef>
<paramdef > sd_event_source *<parameter > source</parameter> </paramdef>
<paramdef > void *<parameter > userdata</parameter> </paramdef>
</funcprototype>
<funcprototype >
<funcdef > void* <function > sd_event_source_get_userdata</function> </funcdef>
<paramdef > sd_event_source *<parameter > source</parameter> </paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1 >
<title > Description</title>
<para > <function > sd_event_source_set_userdata()</function> may be
used to set an arbitrary user data pointer for the event source
object specified as <parameter > source</parameter> . The user data
pointer is usually specified when creating an event source object
with calls such as
<citerefentry > <refentrytitle > sd_event_add_io</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry>
or
<citerefentry > <refentrytitle > sd_event_add_time</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> ,
and may be updated with this call. The user data pointer is also
passed to all handler callback functions associated with the event
source. The <parameter > userdata</parameter> parameter specifies
the new user data pointer to set, the function returns the
previous user data pointer. Note that <constant > NULL</constant> is
a valid user data pointer.</para>
<para > <function > sd_event_source_get_userdata()</function> may be
used to query the current user data pointer assigned to the event
source object <parameter > source</parameter> .</para>
</refsect1>
<refsect1 >
<title > Return Value</title>
<para > On success,
<function > sd_event_source_set_userdata()</function> and
<function > sd_event_source_get_userdata()</function> return the
previously set user data pointer. On failure, they return
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<constant > NULL</constant> .</para>
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</refsect1>
<xi:include href= "libsystemd-pkgconfig.xml" />
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<refsect1 >
<title > History</title>
<para > <function > sd_event_source_get_userdata()</function> was added in version 229.</para>
<para > <function > sd_event_source_set_userdata()</function> was added in version 229.</para>
</refsect1>
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<refsect1 >
<title > See Also</title>
<para >
<citerefentry > <refentrytitle > sd-event</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> ,
<citerefentry > <refentrytitle > sd_event_add_io</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> ,
<citerefentry > <refentrytitle > sd_event_add_time</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> ,
<citerefentry > <refentrytitle > sd_event_add_signal</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> ,
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<citerefentry > <refentrytitle > sd_event_add_child</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> ,
<citerefentry > <refentrytitle > sd_event_add_inotify</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> ,
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<citerefentry > <refentrytitle > sd_event_add_defer</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> ,
<citerefentry > <refentrytitle > sd_event_source_set_description</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry>
</para>
</refsect1>
</refentry>