<?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 2015 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_source_set_enabled" xmlns:xi="http://www.w3.org/2001/XInclude"> <refentryinfo> <title>sd_event_source_set_enabled</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_source_set_enabled</refentrytitle> <manvolnum>3</manvolnum> </refmeta> <refnamediv> <refname>sd_event_source_set_enabled</refname> <refname>sd_event_source_get_enabled</refname> <refname>SD_EVENT_ON</refname> <refname>SD_EVENT_OFF</refname> <refname>SD_EVENT_ONESHOT</refname> <refpurpose>Enable or disable event sources</refpurpose> </refnamediv> <refsynopsisdiv> <funcsynopsis> <funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo> <funcsynopsisinfo><token>enum</token> { <constant>SD_EVENT_OFF</constant> = 0, <constant>SD_EVENT_ON</constant> = 1, <constant>SD_EVENT_ONESHOT</constant> = -1, };</funcsynopsisinfo> <funcprototype> <funcdef>int <function>sd_event_source_set_enabled</function></funcdef> <paramdef>sd_event_source *<parameter>source</parameter></paramdef> <paramdef>int <parameter>enabled</parameter></paramdef> </funcprototype> <funcprototype> <funcdef>int <function>sd_event_source_get_enabled</function></funcdef> <paramdef>sd_event_source *<parameter>source</parameter></paramdef> <paramdef>int *<parameter>enabled</parameter></paramdef> </funcprototype> </funcsynopsis> </refsynopsisdiv> <refsect1> <title>Description</title> <para><function>sd_event_source_set_enabled()</function> may be used to enable or disable the event source object specified as <parameter>source</parameter>. The <parameter>enabled</parameter> parameter takes one of <constant>SD_EVENT_ON</constant> (to enable), <constant>SD_EVENT_OFF</constant> (to disable) or <constant>SD_EVENT_ONESHOT</constant>. If invoked with <constant>SD_EVENT_ONESHOT</constant> the event source will be enabled but automatically reset to <constant>SD_EVENT_OFF</constant> after the event source was dispatched once.</para> <para>Event sources that are disabled will not result in event loop wakeups and will not be dispatched, until they are enabled again.</para> <para><function>sd_event_source_get_enabled()</function> may be used to query whether the event source object <parameter>source</parameter> is currently enabled or not. It returns the enablement state in <parameter>enabled</parameter>.</para> <para>Event source objects are enabled when they are first created with calls such as <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>, <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>. However, depending on the event source type they are enabled continously (<constant>SD_EVENT_ON</constant>) or only for a single invocation of the event source handler (<constant>SD_EVENT_ONESHOT</constant>). For details see the respective manual pages.</para> <para>As event source objects stay active and may be dispatched as long as there is at least one reference to them, in many cases it is a good idea to combine a call to <citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> with a prior call to <function>sd_event_source_set_enabled()</function> with <constant>SD_EVENT_OFF</constant>, to ensure the event source is not dispatched again until all other remaining references are dropped.</para> </refsect1> <refsect1> <title>Return Value</title> <para>On success, <function>sd_event_source_set_enabled()</function> and <function>sd_event_source_get_enabled()</function> return a non-negative 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><constant>-EINVAL</constant></term> <listitem><para><parameter>source</parameter> is not a valid pointer to an <structname>sd_event_source</structname> object.</para></listitem> </varlistentry> <varlistentry> <term><constant>-ENOMEM</constant></term> <listitem><para>Not enough memory.</para></listitem> </varlistentry> <varlistentry> <term><constant>-ECHILD</constant></term> <listitem><para>The event loop has been created in a different process.</para></listitem> </varlistentry> </variablelist> </refsect1> <xi:include href="libsystemd-pkgconfig.xml" /> <refsect1> <title>See Also</title> <para> <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_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>, <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>, <citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> </para> </refsect1> </refentry>