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<refentry id= "sd_event_add_defer" conditional= "ENABLE_KDBUS" >
<refentryinfo >
<title > sd_event_add_defer</title>
<productname > systemd</productname>
<authorgroup >
<author >
<contrib > More text</contrib>
<firstname > Zbigniew</firstname>
<surname > Jędrzejewski-Szmek</surname>
<email > zbyszek@in.waw.pl</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta >
<refentrytitle > sd_event_add_defer</refentrytitle>
<manvolnum > 3</manvolnum>
</refmeta>
<refnamediv >
<refname > sd_event_add_defer</refname>
<refname > sd_event_add_post</refname>
<refname > sd_event_add_exit</refname>
<refpurpose > Add static event sources to an event loop</refpurpose>
</refnamediv>
<refsynopsisdiv >
<funcsynopsis >
<funcsynopsisinfo > #include < systemd/sd-bus.h> </funcsynopsisinfo>
<funcprototype >
<funcdef > int <function > sd_event_add_defer</function> </funcdef>
<paramdef > sd_event *<parameter > event</parameter> </paramdef>
<paramdef > sd_event_source **<parameter > source</parameter> </paramdef>
<paramdef > sd_event_handler_t <parameter > handler</parameter> </paramdef>
<paramdef > void *<parameter > userdata</parameter> </paramdef>
</funcprototype>
<funcprototype >
<funcdef > int <function > sd_event_add_post</function> </funcdef>
<paramdef > sd_event *<parameter > event</parameter> </paramdef>
<paramdef > sd_event_source **<parameter > source</parameter> </paramdef>
<paramdef > sd_event_handler_t <parameter > handler</parameter> </paramdef>
<paramdef > void *<parameter > userdata</parameter> </paramdef>
</funcprototype>
<funcprototype >
<funcdef > int <function > sd_event_add_exit</function> </funcdef>
<paramdef > sd_event *<parameter > event</parameter> </paramdef>
<paramdef > sd_event_source **<parameter > source</parameter> </paramdef>
<paramdef > sd_event_handler_t <parameter > handler</parameter> </paramdef>
<paramdef > void *<parameter > userdata</parameter> </paramdef>
</funcprototype>
<funcprototype >
<funcdef > typedef int (*<function > sd_event_handler_t</function> )</funcdef>
<paramdef > sd_event_source *<parameter > s</parameter> </paramdef>
<paramdef > void *<parameter > userdata</parameter> </paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1 >
<title > Description</title>
<para > Those three functions add new event sources to an event loop
object. The event loop is specified in
<parameter > event</parameter> , the event source is returned in the
<parameter > source</parameter> parameter. The event sources are
enabled statically and will "fire" when the event loop is run and
the conditions described below are met. The handler function will
be passed the <parameter > userdata</parameter> pointer, which may
be chosen freely by the caller.</para>
<para > <function > sd_event_add_defer()</function> adds a new event
source that will "fire" the next time the event loop is run. By
default, the handler will be called once
(<constant > SD_EVENT_ONESHOT</constant> ).</para>
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<para > <function > sd_event_add_post()</function> adds a new event
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source that will "fire" if any event handlers are invoked whenever
the event loop is run. By default, the source is enabled
permanently (<constant > SD_EVENT_ON</constant> ).</para>
<para > <function > sd_event_add_exit()</function> adds a new event
source that will "fire" when the event loop is terminated
with <function > sd_event_exit()</function> .</para>
<para > The
<citerefentry > <refentrytitle > sd_event_source_set_enabled</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry>
function may be used to enable the event source permanently
(<constant > SD_EVENT_ON</constant> ) or to make it fire just once
(<constant > SD_EVENT_ONESHOT</constant> ). If the handler function
returns a negative error code, it will be disabled after the
invocation, even if <constant > SD_EVENT_ON</constant> mode is
set.</para>
</refsect1>
<refsect1 >
<title > Return Value</title>
<para > On success, this functions return 0 or a positive
integer. On failure, they return a negative errno-style error
code.</para>
</refsect1>
<refsect1 >
<title > Errors</title>
<para > Returned errors may indicate the following problems:</para>
<variablelist >
<varlistentry >
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<term > <constant > -ENOMEM</constant> </term>
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<listitem > <para > Not enough memory to allocate an object.</para> </listitem>
</varlistentry>
<varlistentry >
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<term > <constant > -EINVAL</constant> </term>
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<listitem > <para > An invalid argument has been passed.</para> </listitem>
</varlistentry>
<varlistentry >
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<term > <constant > -ESTALE</constant> </term>
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<listitem > <para > The event loop is already terminated.</para> </listitem>
</varlistentry>
<varlistentry >
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<term > <constant > -ECHILD</constant> </term>
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<listitem > <para > The event loop has been created in a different process.</para> </listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 >
<title > Notes</title>
<para > Functions described here are available as a shared library,
which can be compiled and linked to with the
<constant > libsystemd</constant> <citerefentry
project='die-net'><refentrytitle > pkg-config</refentrytitle> <manvolnum > 1</manvolnum> </citerefentry>
file.</para>
</refsect1>
<refsect1 >
<title > See Also</title>
<para >
<citerefentry > <refentrytitle > systemd</refentrytitle> <manvolnum > 1</manvolnum> </citerefentry> ,
<citerefentry > <refentrytitle > sd-event</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> ,
<citerefentry > <refentrytitle > sd_event_new</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> ,
<citerefentry > <refentrytitle > sd_event_add_child</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> ,
<citerefentry > <refentrytitle > sd_event_source_set_enabled</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry>
</para>
</refsect1>
</refentry>