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182 lines
7.0 KiB
XML
182 lines
7.0 KiB
XML
<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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This file is part of systemd.
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Copyright 2014 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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-->
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<refentry id="sd_event_new" conditional="ENABLE_KDBUS">
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<refentryinfo>
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<title>sd_event_new</title>
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<productname>systemd</productname>
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<authorgroup>
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<author>
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<contrib>Developer</contrib>
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<firstname>Lennart</firstname>
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<surname>Poettering</surname>
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<email>lennart@poettering.net</email>
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</author>
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</authorgroup>
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</refentryinfo>
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<refmeta>
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<refentrytitle>sd_event_new</refentrytitle>
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<manvolnum>3</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>sd_event_new</refname>
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<refname>sd_event_default</refname>
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<refname>sd_event_ref</refname>
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<refname>sd_event_unref</refname>
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<refpurpose>Acquire and release an event loop object</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
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<funcprototype>
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<funcdef>int <function>sd_event_new</function></funcdef>
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<paramdef>sd_bus **<parameter>event</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_event_default</function></funcdef>
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<paramdef>sd_bus **<parameter>event</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>sd_bus *<function>sd_event_ref</function></funcdef>
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<paramdef>sd_bus *<parameter>event</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>sd_bus *<function>sd_event_unref</function></funcdef>
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<paramdef>sd_bus *<parameter>event</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><function>sd_event_new()</function> allocates a new event
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loop object. The event loop object is returned in the
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<parameter>event</parameter> parameter. After use, drop
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the returned reference with
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<function>sd_event_unref()</function>. When the last reference is
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dropped, the object is freed.</para>
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<para><function>sd_event_default()</function> acquires a reference
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to the default event loop object of the calling thread, possibly
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allocating a new object if no default event loop object has been
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allocated yet for the thread. After use, drop the returned
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reference with <function>sd_event_unref()</function>. When the
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last reference is dropped, the event loop is freed. If this
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function is called while the object returned from a previous call
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from the same thread is still referenced, the same object is
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returned again, but the reference is increased by one. It is
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recommended to use this call instead of
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<function>sd_event_new()</function> in order to share event loop
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objects between various components that are dispatched in the same
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thread. All threads have exactly either zero or one default event loop
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objects associated, but never more.</para>
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<para><function>sd_event_ref()</function> increases the reference
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count of the specified event loop object by one.</para>
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<para><function>sd_event_unref()</function> decreases the
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reference count of the specified event loop object by one. If
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the count hits zero, the object is freed. Note that it
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is freed regardless of whether it is the default event loop object for a
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thread or not. This means that allocating an event loop with
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<function>sd_event_default()</function>, then releasing it, and
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then acquiring a new one with
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<function>sd_event_default()</function> will result in two
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distinct objects. Note that in order to free an event loop object,
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all remaining event sources of the event loop also need to be
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freed as each keeps a reference to it.</para>
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</refsect1>
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<refsect1>
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<title>Return Value</title>
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<para>On success, <function>sd_event_new()</function> and
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<function>sd_event_default()</function> return 0 or a positive
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integer. On failure, they return a negative errno-style error
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code. <function>sd_event_ref()</function> always returns a pointer
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to the event loop object passed
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in. <function>sd_event_unref()</function> always returns
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<constant>NULL</constant>.</para>
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</refsect1>
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<refsect1>
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<title>Errors</title>
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<para>Returned errors may indicate the following problems:</para>
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<variablelist>
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<varlistentry>
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<term><constant>-ENOMEM</constant></term>
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<listitem><para>Not enough memory to allocate the object.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-EMFILE</constant></term>
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<listitem><para>The maximum number of event loops has been allocated.</para></listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Notes</title>
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<para><function>sd_event_new()</function> and the other functions
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described here are available as a shared library, which can be
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compiled and linked to with the
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<constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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file.</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<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>,
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<citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_add_post</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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