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+
8 This file is part of systemd.
10 Copyright 2015 Lennart Poettering
13 <refentry id=
"sd_event_source_set_enabled" xmlns:
xi=
"http://www.w3.org/2001/XInclude">
16 <title>sd_event_source_set_enabled
</title>
17 <productname>systemd
</productname>
21 <contrib>Developer
</contrib>
22 <firstname>Lennart
</firstname>
23 <surname>Poettering
</surname>
24 <email>lennart@poettering.net
</email>
30 <refentrytitle>sd_event_source_set_enabled
</refentrytitle>
31 <manvolnum>3</manvolnum>
35 <refname>sd_event_source_set_enabled
</refname>
36 <refname>sd_event_source_get_enabled
</refname>
37 <refname>SD_EVENT_ON
</refname>
38 <refname>SD_EVENT_OFF
</refname>
39 <refname>SD_EVENT_ONESHOT
</refname>
41 <refpurpose>Enable or disable event sources
</refpurpose>
46 <funcsynopsisinfo>#include
<systemd/sd-event.h
></funcsynopsisinfo>
48 <funcsynopsisinfo><token>enum
</token> {
49 <constant>SD_EVENT_OFF
</constant> =
0,
50 <constant>SD_EVENT_ON
</constant> =
1,
51 <constant>SD_EVENT_ONESHOT
</constant> = -
1,
55 <funcdef>int
<function>sd_event_source_set_enabled
</function></funcdef>
56 <paramdef>sd_event_source *
<parameter>source
</parameter></paramdef>
57 <paramdef>int
<parameter>enabled
</parameter></paramdef>
61 <funcdef>int
<function>sd_event_source_get_enabled
</function></funcdef>
62 <paramdef>sd_event_source *
<parameter>source
</parameter></paramdef>
63 <paramdef>int *
<parameter>enabled
</parameter></paramdef>
70 <title>Description
</title>
72 <para><function>sd_event_source_set_enabled()
</function> may be
73 used to enable or disable the event source object specified as
74 <parameter>source
</parameter>. The
<parameter>enabled
</parameter>
75 parameter takes one of
<constant>SD_EVENT_ON
</constant> (to
76 enable),
<constant>SD_EVENT_OFF
</constant> (to disable) or
77 <constant>SD_EVENT_ONESHOT
</constant>. If invoked with
78 <constant>SD_EVENT_ONESHOT
</constant> the event source will be
79 enabled but automatically reset to
80 <constant>SD_EVENT_OFF
</constant> after the event source was
81 dispatched once.
</para>
83 <para>Event sources that are disabled will not result in event
84 loop wakeups and will not be dispatched, until they are enabled
87 <para><function>sd_event_source_get_enabled()
</function> may be
88 used to query whether the event source object
89 <parameter>source
</parameter> is currently enabled or not. It
90 returns the enablement state in
91 <parameter>enabled
</parameter>.
</para>
93 <para>Event source objects are enabled when they are first created
95 <citerefentry><refentrytitle>sd_event_add_io
</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
96 <citerefentry><refentrytitle>sd_event_add_time
</refentrytitle><manvolnum>3</manvolnum></citerefentry>. However,
97 depending on the event source type they are enabled continuously
98 (
<constant>SD_EVENT_ON
</constant>) or only for a single invocation
99 of the event source handler
100 (
<constant>SD_EVENT_ONESHOT
</constant>). For details see the
101 respective manual pages.
</para>
103 <para>As event source objects stay active and may be dispatched as
104 long as there is at least one reference to them, in many cases it
105 is a good idea to combine a call to
106 <citerefentry><refentrytitle>sd_event_source_unref
</refentrytitle><manvolnum>3</manvolnum></citerefentry>
108 <function>sd_event_source_set_enabled()
</function> with
109 <constant>SD_EVENT_OFF
</constant>, to ensure the event source is
110 not dispatched again until all other remaining references are dropped.
</para>
114 <title>Return Value
</title>
116 <para>On success,
<function>sd_event_source_set_enabled()
</function> and
117 <function>sd_event_source_get_enabled()
</function> return a
118 non-negative integer. On failure, they return a negative
119 errno-style error code.
</para>
123 <title>Errors
</title>
125 <para>Returned errors may indicate the following problems:
</para>
129 <term><constant>-EINVAL
</constant></term>
131 <listitem><para><parameter>source
</parameter> is not a valid
132 pointer to an
<structname>sd_event_source
</structname>
133 object.
</para></listitem>
137 <term><constant>-ENOMEM
</constant></term>
139 <listitem><para>Not enough memory.
</para></listitem>
143 <term><constant>-ECHILD
</constant></term>
145 <listitem><para>The event loop has been created in a different process.
</para></listitem>
152 <xi:include href=
"libsystemd-pkgconfig.xml" />
155 <title>See Also
</title>
158 <citerefentry><refentrytitle>sd-event
</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
159 <citerefentry><refentrytitle>sd_event_add_io
</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
160 <citerefentry><refentrytitle>sd_event_add_time
</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
161 <citerefentry><refentrytitle>sd_event_add_child
</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
162 <citerefentry><refentrytitle>sd_event_add_signal
</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
163 <citerefentry><refentrytitle>sd_event_add_defer
</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
164 <citerefentry><refentrytitle>sd_event_source_unref
</refentrytitle><manvolnum>3</manvolnum></citerefentry>