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<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
<!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 Lennart Poettering
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_new">
<refentryinfo>
<title>sd_event_new</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>Developer</contrib>
<firstname>Lennart</firstname>
<surname>Poettering</surname>
<email>lennart@poettering.net</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>sd_event_new</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>sd_event_new</refname>
<refname>sd_event_default</refname>
<refname>sd_event_ref</refname>
<refname>sd_event_unref</refname>
<refpurpose>Acquire and release an event loop object</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
<funcprototype>
<funcdef>int <function>sd_event_new</function></funcdef>
<paramdef>sd_bus **<parameter>event</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_event_default</function></funcdef>
<paramdef>sd_bus **<parameter>event</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>sd_bus *<function>sd_event_ref</function></funcdef>
<paramdef>sd_bus *<parameter>event</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>sd_bus *<function>sd_event_unref</function></funcdef>
<paramdef>sd_bus *<parameter>event</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><function>sd_event_new()</function> allocates a new event
loop object. The event loop object is returned in the
<parameter>event</parameter> parameter. After use, drop
the returned reference with
<function>sd_event_unref()</function>. When the last reference is
dropped, the object is freed.</para>
<para><function>sd_event_default()</function> acquires a reference
to the default event loop object of the calling thread, possibly
allocating a new object if no default event loop object has been
allocated yet for the thread. After use, drop the returned
reference with <function>sd_event_unref()</function>. When the
last reference is dropped, the event loop is freed. If this
function is called while the object returned from a previous call
from the same thread is still referenced, the same object is
returned again, but the reference is increased by one. It is
recommended to use this call instead of
<function>sd_event_new()</function> in order to share event loop
objects between various components that are dispatched in the same
thread. All threads have exactly either zero or one default event loop
objects associated, but never more.</para>
<para><function>sd_event_ref()</function> increases the reference
count of the specified event loop object by one.</para>
<para><function>sd_event_unref()</function> decreases the
reference count of the specified event loop object by one. If
the count hits zero, the object is freed. Note that it
is freed regardless of whether it is the default event loop object for a
thread or not. This means that allocating an event loop with
<function>sd_event_default()</function>, then releasing it, and
then acquiring a new one with
<function>sd_event_default()</function> will result in two
distinct objects. Note that in order to free an event loop object,
all remaining event sources of the event loop also need to be
freed as each keeps a reference to it.</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para>On success, <function>sd_event_new()</function> and
<function>sd_event_default()</function> return 0 or a positive
integer. On failure, they return a negative errno-style error
code. <function>sd_event_ref()</function> always returns a pointer
to the event loop object passed
in. <function>sd_event_unref()</function> always returns
<constant>NULL</constant>.</para>
</refsect1>
<refsect1>
<title>Errors</title>
<para>Returned errors may indicate the following problems:</para>
<variablelist>
<varlistentry>
<term><constant>-ENOMEM</constant></term>
<listitem><para>Not enough memory to allocate the object.</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>-EMFILE</constant></term>
<listitem><para>The maximum number of event loops has been allocated.</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Notes</title>
<para><function>sd_event_new()</function> and the other 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_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>,
<citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_event_add_post</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
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