1 <?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
6 SPDX-License-Identifier: LGPL-2.1+
9 <refentry id="sd_event_source_set_enabled" xmlns:xi="http://www.w3.org/2001/XInclude">
12 <title>sd_event_source_set_enabled</title>
13 <productname>elogind</productname>
17 <contrib>Developer</contrib>
18 <firstname>Lennart</firstname>
19 <surname>Poettering</surname>
20 <email>lennart@poettering.net</email>
26 <refentrytitle>sd_event_source_set_enabled</refentrytitle>
27 <manvolnum>3</manvolnum>
31 <refname>sd_event_source_set_enabled</refname>
32 <refname>sd_event_source_get_enabled</refname>
33 <refname>SD_EVENT_ON</refname>
34 <refname>SD_EVENT_OFF</refname>
35 <refname>SD_EVENT_ONESHOT</refname>
37 <refpurpose>Enable or disable event sources</refpurpose>
42 <funcsynopsisinfo>#include <elogind/sd-event.h></funcsynopsisinfo>
44 <funcsynopsisinfo><token>enum</token> {
45 <constant>SD_EVENT_OFF</constant> = 0,
46 <constant>SD_EVENT_ON</constant> = 1,
47 <constant>SD_EVENT_ONESHOT</constant> = -1,
51 <funcdef>int <function>sd_event_source_set_enabled</function></funcdef>
52 <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
53 <paramdef>int <parameter>enabled</parameter></paramdef>
57 <funcdef>int <function>sd_event_source_get_enabled</function></funcdef>
58 <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
59 <paramdef>int *<parameter>enabled</parameter></paramdef>
66 <title>Description</title>
68 <para><function>sd_event_source_set_enabled()</function> may be
69 used to enable or disable the event source object specified as
70 <parameter>source</parameter>. The <parameter>enabled</parameter>
71 parameter takes one of <constant>SD_EVENT_ON</constant> (to
72 enable), <constant>SD_EVENT_OFF</constant> (to disable) or
73 <constant>SD_EVENT_ONESHOT</constant>. If invoked with
74 <constant>SD_EVENT_ONESHOT</constant> the event source will be
75 enabled but automatically reset to
76 <constant>SD_EVENT_OFF</constant> after the event source was
77 dispatched once.</para>
79 <para>Event sources that are disabled will not result in event
80 loop wakeups and will not be dispatched, until they are enabled
83 <para><function>sd_event_source_get_enabled()</function> may be
84 used to query whether the event source object
85 <parameter>source</parameter> is currently enabled or not. It
86 returns the enablement state in
87 <parameter>enabled</parameter>.</para>
89 <para>Event source objects are enabled when they are first created
91 <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
92 <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>. However,
93 depending on the event source type they are enabled continuously
94 (<constant>SD_EVENT_ON</constant>) or only for a single invocation
95 of the event source handler
96 (<constant>SD_EVENT_ONESHOT</constant>). For details see the
97 respective manual pages.</para>
99 <para>As event source objects stay active and may be dispatched as
100 long as there is at least one reference to them, in many cases it
101 is a good idea to combine a call to
102 <citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>
104 <function>sd_event_source_set_enabled()</function> with
105 <constant>SD_EVENT_OFF</constant>, to ensure the event source is
106 not dispatched again until all other remaining references are dropped.</para>
110 <title>Return Value</title>
112 <para>On success, <function>sd_event_source_set_enabled()</function> and
113 <function>sd_event_source_get_enabled()</function> return a
114 non-negative integer. On failure, they return a negative
115 errno-style error code.</para>
119 <title>Errors</title>
121 <para>Returned errors may indicate the following problems:</para>
125 <term><constant>-EINVAL</constant></term>
127 <listitem><para><parameter>source</parameter> is not a valid
128 pointer to an <structname>sd_event_source</structname>
129 object.</para></listitem>
133 <term><constant>-ENOMEM</constant></term>
135 <listitem><para>Not enough memory.</para></listitem>
139 <term><constant>-ECHILD</constant></term>
141 <listitem><para>The event loop has been created in a different process.</para></listitem>
148 <xi:include href="libelogind-pkgconfig.xml" />
151 <title>See Also</title>
154 <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
155 <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
156 <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
157 <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
158 <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
159 <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
160 <citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>