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514094f9 | 1 | <?xml version='1.0'?> |
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2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" |
3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> | |
4 | ||
5 | <!-- | |
572eb058 | 6 | SPDX-License-Identifier: LGPL-2.1+ |
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7 | --> |
8 | ||
9 | <refentry id="sd_event_source_set_enabled" xmlns:xi="http://www.w3.org/2001/XInclude"> | |
10 | ||
11 | <refentryinfo> | |
12 | <title>sd_event_source_set_enabled</title> | |
13 | <productname>systemd</productname> | |
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14 | </refentryinfo> |
15 | ||
16 | <refmeta> | |
17 | <refentrytitle>sd_event_source_set_enabled</refentrytitle> | |
18 | <manvolnum>3</manvolnum> | |
19 | </refmeta> | |
20 | ||
21 | <refnamediv> | |
22 | <refname>sd_event_source_set_enabled</refname> | |
23 | <refname>sd_event_source_get_enabled</refname> | |
24 | <refname>SD_EVENT_ON</refname> | |
25 | <refname>SD_EVENT_OFF</refname> | |
26 | <refname>SD_EVENT_ONESHOT</refname> | |
27 | ||
28 | <refpurpose>Enable or disable event sources</refpurpose> | |
29 | </refnamediv> | |
30 | ||
31 | <refsynopsisdiv> | |
32 | <funcsynopsis> | |
33 | <funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo> | |
34 | ||
35 | <funcsynopsisinfo><token>enum</token> { | |
36 | <constant>SD_EVENT_OFF</constant> = 0, | |
37 | <constant>SD_EVENT_ON</constant> = 1, | |
38 | <constant>SD_EVENT_ONESHOT</constant> = -1, | |
39 | };</funcsynopsisinfo> | |
40 | ||
41 | <funcprototype> | |
42 | <funcdef>int <function>sd_event_source_set_enabled</function></funcdef> | |
43 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
44 | <paramdef>int <parameter>enabled</parameter></paramdef> | |
45 | </funcprototype> | |
46 | ||
47 | <funcprototype> | |
48 | <funcdef>int <function>sd_event_source_get_enabled</function></funcdef> | |
49 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
50 | <paramdef>int *<parameter>enabled</parameter></paramdef> | |
51 | </funcprototype> | |
52 | ||
53 | </funcsynopsis> | |
54 | </refsynopsisdiv> | |
55 | ||
56 | <refsect1> | |
57 | <title>Description</title> | |
58 | ||
59 | <para><function>sd_event_source_set_enabled()</function> may be | |
60 | used to enable or disable the event source object specified as | |
61 | <parameter>source</parameter>. The <parameter>enabled</parameter> | |
62 | parameter takes one of <constant>SD_EVENT_ON</constant> (to | |
63 | enable), <constant>SD_EVENT_OFF</constant> (to disable) or | |
64 | <constant>SD_EVENT_ONESHOT</constant>. If invoked with | |
65 | <constant>SD_EVENT_ONESHOT</constant> the event source will be | |
66 | enabled but automatically reset to | |
67 | <constant>SD_EVENT_OFF</constant> after the event source was | |
68 | dispatched once.</para> | |
69 | ||
70 | <para>Event sources that are disabled will not result in event | |
71 | loop wakeups and will not be dispatched, until they are enabled | |
72 | again.</para> | |
73 | ||
74 | <para><function>sd_event_source_get_enabled()</function> may be | |
75 | used to query whether the event source object | |
76 | <parameter>source</parameter> is currently enabled or not. It | |
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77 | returns the enablement state (one of <constant>SD_EVENT_ON</constant>, |
78 | <constant>SD_EVENT_OFF</constant>, <constant>SD_EVENT_ONESHOT</constant>) | |
79 | in <parameter>enabled</parameter>, if it is not <constant>NULL</constant>. | |
80 | It also returns true if the event source is not disabled.</para> | |
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81 | |
82 | <para>Event source objects are enabled when they are first created | |
83 | with calls such as | |
84 | <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
85 | <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>. However, | |
7f3fdb7f | 86 | depending on the event source type they are enabled continuously |
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87 | (<constant>SD_EVENT_ON</constant>) or only for a single invocation |
88 | of the event source handler | |
89 | (<constant>SD_EVENT_ONESHOT</constant>). For details see the | |
90 | respective manual pages.</para> | |
91 | ||
92 | <para>As event source objects stay active and may be dispatched as | |
93 | long as there is at least one reference to them, in many cases it | |
94 | is a good idea to combine a call to | |
95 | <citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
96 | with a prior call to | |
97 | <function>sd_event_source_set_enabled()</function> with | |
98 | <constant>SD_EVENT_OFF</constant>, to ensure the event source is | |
99 | not dispatched again until all other remaining references are dropped.</para> | |
100 | </refsect1> | |
101 | ||
102 | <refsect1> | |
103 | <title>Return Value</title> | |
104 | ||
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105 | <para>On success, <function>sd_event_source_set_enabled()</function> returns a non-negative |
106 | integer. <function>sd_event_source_get_enabled()</function> returns zero if the source is | |
107 | disabled (<constant>SD_EVENT_OFF</constant>) and a positive integer otherwise. On failure, they | |
108 | return a negative errno-style error code.</para> | |
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109 | </refsect1> |
110 | ||
111 | <refsect1> | |
112 | <title>Errors</title> | |
113 | ||
114 | <para>Returned errors may indicate the following problems:</para> | |
115 | ||
116 | <variablelist> | |
117 | <varlistentry> | |
118 | <term><constant>-EINVAL</constant></term> | |
119 | ||
120 | <listitem><para><parameter>source</parameter> is not a valid | |
121 | pointer to an <structname>sd_event_source</structname> | |
122 | object.</para></listitem> | |
123 | </varlistentry> | |
124 | ||
125 | <varlistentry> | |
126 | <term><constant>-ENOMEM</constant></term> | |
127 | ||
128 | <listitem><para>Not enough memory.</para></listitem> | |
129 | </varlistentry> | |
130 | ||
131 | <varlistentry> | |
132 | <term><constant>-ECHILD</constant></term> | |
133 | ||
134 | <listitem><para>The event loop has been created in a different process.</para></listitem> | |
135 | ||
136 | </varlistentry> | |
137 | ||
138 | </variablelist> | |
139 | </refsect1> | |
140 | ||
141 | <xi:include href="libsystemd-pkgconfig.xml" /> | |
142 | ||
143 | <refsect1> | |
144 | <title>See Also</title> | |
145 | ||
146 | <para> | |
147 | <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
148 | <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
149 | <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
dc83f27a | 150 | <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
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151 | <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
152 | <citerefentry><refentrytitle>sd_event_add_inotify</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
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153 | <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
154 | <citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
155 | </para> | |
156 | </refsect1> | |
157 | ||
158 | </refentry> |