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<?xml version='1.0'?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
<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>
</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>ret</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 one dispatch.
For <constant>SD_EVENT_OFF</constant>, the event source <parameter>source</parameter> may be
<constant>NULL</constant>, in which case the function does nothing. Otherwise,
<parameter>source</parameter> must be a valid pointer to an <structname>sd_event_source</structname>
object.</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. If both the
<parameter>source</parameter> and the output parameter <parameter>ret</parameter> are
<constant>NULL</constant>, this function returns false. Otherwise, <parameter>source</parameter> must be
a valid pointer to an <structname>sd_event_source</structname> object. If the output parameter
<parameter>ret</parameter> is not <constant>NULL</constant>, it is set to the enablement state (one
of <constant>SD_EVENT_ON</constant>, <constant>SD_EVENT_OFF</constant>,
<constant>SD_EVENT_ONESHOT</constant>). The function also returns true if the event source is not
disabled.</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 continuously
(<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> returns a non-negative
integer. <function>sd_event_source_get_enabled()</function> returns zero if the source is disabled
(<constant>SD_EVENT_OFF</constant>) and a positive integer otherwise. On failure, they return a negative
errno-style error code.</para>
<refsect2>
<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, library or module instance.</para></listitem>
</varlistentry>
</variablelist>
</refsect2>
</refsect1>
<xi:include href="libsystemd-pkgconfig.xml" />
<refsect1>
<title>History</title>
<para><function>sd_event_source_set_enabled()</function> and
<function>sd_event_source_get_enabled()</function> were added in version 229.</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para><simplelist type="inline">
<member><citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>sd_event_add_inotify</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>sd_event_source_set_ratelimit</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
</simplelist></para>
</refsect1>
</refentry>
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