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Also, document this functionality more prominently, including with a reference from sd_event_exit(). This is mostly to make things complete, as previously we supported NULL callbacks only in _add_time() and _add_signal(). However, I think this makes snese for IO event sources too (think: when some fd such as a pipe end sees SIGHUP or so, exit), as well as defer or post event sources (i.e. exit once we got nothing else to do). This also adds support for inotify event sources, simply to complete things (I can't see the immediate use, but maybe someone else comes up with it). The only event source type that doesn't allow callback=NULL now are exit callbacks, but for them they make little sense, as the event loop is exiting then anyway.
151 lines
6.1 KiB
XML
151 lines
6.1 KiB
XML
<?xml version='1.0'?>
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1+ -->
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<refentry id="sd_event_exit" xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>sd_event_exit</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>sd_event_exit</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_exit</refname>
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<refname>sd_event_get_exit_code</refname>
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<refpurpose>Ask the event loop to exit</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo>
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<funcprototype>
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<funcdef>int <function>sd_event_exit</function></funcdef>
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<paramdef>sd_event *<parameter>event</parameter></paramdef>
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<paramdef>int <parameter>code</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_event_get_exit_code</function></funcdef>
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<paramdef>sd_event *<parameter>event</parameter></paramdef>
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<paramdef>int *<parameter>code</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_exit()</function> requests the event loop
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specified in the <parameter>event</parameter> event loop object to
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exit. The <parameter>code</parameter> parameter may be any integer
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value and is returned as-is by
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<citerefentry><refentrytitle>sd_event_loop</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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after the last event loop iteration. It may also be queried
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using <function>sd_event_get_exit_code()</function>, see
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below. </para>
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<para>When exiting is requested the event loop will stop listening
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for and dispatching regular event sources. Instead it will proceed
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with executing only event sources registered with
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<citerefentry><refentrytitle>sd_event_add_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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in the order defined by their priority. After all exit event
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sources have been dispatched the event loop is terminated.</para>
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<para>If <function>sd_event_exit()</function> is invoked a second
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time while the event loop is still processing exit event sources,
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the exit code stored in the event loop object is updated, but
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otherwise no further operation is executed.</para>
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<para><function>sd_event_get_exit_code()</function> may be used to
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query the exit code passed into
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<function>sd_event_exit()</function> earlier.</para>
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<para>While the full positive and negative integer ranges may be used
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for the exit code, care should be taken not pick exit codes that
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conflict with regular exit codes returned by
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<function>sd_event_loop()</function>, if these exit codes shall be
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distinguishable.</para>
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<para>Note that for most event source types passing the callback pointer as <constant>NULL</constant> in
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the respective constructor call (i.e. in
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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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…) has the effect of <function>sd_event_exit()</function> being invoked once the event source triggers,
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with the specified userdata pointer cast to an integer as the exit code parameter. This is useful to
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automatically terminate an event loop after some condition, such as a time-out or reception of
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<constant>SIGTERM</constant> or similar. See the documentation for the respective constructor call for
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details.</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_exit()</function> and <function>sd_event_get_exit_code()</function>
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return 0 or a positive integer. On failure, they return a negative errno-style error code.</para>
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<refsect2>
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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>-EINVAL</constant></term>
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<listitem><para>The event loop object or error code pointer are invalid.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-ECHILD</constant></term>
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<listitem><para>The event loop was created in a different process.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-ESTALE</constant></term>
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<listitem><para>The event loop has exited already and all exit handlers are already processed.
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</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-ENODATA</constant></term>
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<listitem><para>The event loop has not been requested to exit yet.</para></listitem>
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</varlistentry>
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</variablelist>
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</refsect2>
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</refsect1>
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<xi:include href="libsystemd-pkgconfig.xml" />
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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_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_add_exit</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_io</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_inotify</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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