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<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
This file is part of systemd.
Copyright 2014 Zbigniew Jędrzejewski-Szmek
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->
<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>
<para><function>sd_event_add_defer()</function> adds a new event
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>
<term><varname>-ENOMEM</varname></term>
<listitem><para>Not enough memory to allocate an object.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>-EINVAL</varname></term>
<listitem><para>An invalid argument has been passed.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>-ESTALE</varname></term>
<listitem><para>The event loop is already terminated.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>-ECHILD</varname></term>
<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>
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