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514094f9 | 1 | <?xml version='1.0'?> |
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2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" |
3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> | |
0307f791 | 4 | <!-- SPDX-License-Identifier: LGPL-2.1+ --> |
3144ebca | 5 | |
dc83f27a | 6 | <refentry id="sd_event_add_signal" xmlns:xi="http://www.w3.org/2001/XInclude"> |
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7 | |
8 | <refentryinfo> | |
9 | <title>sd_event_add_signal</title> | |
10 | <productname>systemd</productname> | |
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11 | </refentryinfo> |
12 | ||
13 | <refmeta> | |
14 | <refentrytitle>sd_event_add_signal</refentrytitle> | |
15 | <manvolnum>3</manvolnum> | |
16 | </refmeta> | |
17 | ||
18 | <refnamediv> | |
19 | <refname>sd_event_add_signal</refname> | |
20 | <refname>sd_event_source_get_signal</refname> | |
dc83f27a | 21 | <refname>sd_event_signal_handler_t</refname> |
3144ebca | 22 | |
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23 | <refpurpose>Add a UNIX process signal event source to an event |
24 | loop</refpurpose> | |
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25 | </refnamediv> |
26 | ||
27 | <refsynopsisdiv> | |
28 | <funcsynopsis> | |
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29 | <funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo> |
30 | ||
31 | <funcsynopsisinfo><token>typedef</token> struct sd_event_source sd_event_source;</funcsynopsisinfo> | |
32 | ||
33 | <funcprototype> | |
34 | <funcdef>typedef int (*<function>sd_event_signal_handler_t</function>)</funcdef> | |
35 | <paramdef>sd_event_source *<parameter>s</parameter></paramdef> | |
36 | <paramdef>const struct signalfd_siginfo *<parameter>si</parameter></paramdef> | |
37 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
38 | </funcprototype> | |
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39 | |
40 | <funcprototype> | |
41 | <funcdef>int <function>sd_event_add_signal</function></funcdef> | |
42 | <paramdef>sd_event *<parameter>event</parameter></paramdef> | |
43 | <paramdef>sd_event_source **<parameter>source</parameter></paramdef> | |
44 | <paramdef>int <parameter>signal</parameter></paramdef> | |
45 | <paramdef>sd_event_signal_handler_t <parameter>handler</parameter></paramdef> | |
46 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
47 | </funcprototype> | |
48 | ||
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49 | <funcprototype> |
50 | <funcdef>int <function>sd_event_source_get_signal</function></funcdef> | |
51 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
52 | </funcprototype> | |
53 | ||
54 | </funcsynopsis> | |
55 | </refsynopsisdiv> | |
56 | ||
57 | <refsect1> | |
58 | <title>Description</title> | |
59 | ||
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60 | <para><function>sd_event_add_signal()</function> adds a new UNIX |
61 | process signal event source to an event loop. The event loop | |
62 | object is specified in the <parameter>event</parameter> parameter, | |
63 | and the event source object is returned in the | |
64 | <parameter>source</parameter> parameter. The | |
65 | <parameter>signal</parameter> parameter specifies the numeric | |
66 | signal to be handled (see <citerefentry | |
67 | project='man-pages'><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry>). | |
68 | The <parameter>handler</parameter> parameter must reference a | |
69 | function to call when the signal is received or be | |
70 | <constant>NULL</constant>. The handler function will be passed | |
71 | the <parameter>userdata</parameter> pointer, which may be chosen | |
3144ebca | 72 | freely by the caller. The handler also receives a pointer to a |
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73 | <structname>signalfd_siginfo</structname> structure containing |
74 | information about the received signal. See <citerefentry | |
75 | project='man-pages'><refentrytitle>signalfd</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
922d948b | 76 | for further information.</para> |
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77 | |
78 | <para>Only a single handler may be installed for a specific | |
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79 | signal. The signal will be unblocked by this call, and must be |
80 | blocked before this function is called in all threads (using | |
81 | <citerefentry | |
82 | project='man-pages'><refentrytitle>sigprocmask</refentrytitle><manvolnum>2</manvolnum></citerefentry>). If | |
83 | the handler is not specified (<parameter>handler</parameter> is | |
3144ebca | 84 | <constant>NULL</constant>), a default handler which causes the |
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85 | program to exit cleanly will be used.</para> |
86 | ||
87 | <para>By default, the event source is enabled permanently | |
88 | (<constant>SD_EVENT_ON</constant>), but this may be changed with | |
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89 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>. |
90 | If the handler function returns a negative error code, it will be | |
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91 | disabled after the invocation, even if the |
92 | <constant>SD_EVENT_ON</constant> mode was requested before. | |
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93 | </para> |
94 | ||
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95 | <para>To destroy an event source object use |
96 | <citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
97 | but note that the event source is only removed from the event loop | |
98 | when all references to the event source are dropped. To make sure | |
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99 | an event source does not fire anymore, even if it is still referenced, |
100 | disable the event source using | |
101 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
102 | with <constant>SD_EVENT_OFF</constant>.</para> | |
dc83f27a | 103 | |
7f3fdb7f | 104 | <para>If the second parameter of |
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105 | <function>sd_event_add_signal()</function> is |
106 | <constant>NULL</constant> no reference to the event source object | |
107 | is returned. In this case the event source is considered | |
108 | "floating", and will be destroyed implicitly when the event loop | |
109 | itself is destroyed.</para> | |
110 | ||
111 | <para><function>sd_event_source_get_signal()</function> returns | |
112 | the configured signal number of an event source created previously | |
113 | with <function>sd_event_add_signal()</function>. It takes the | |
114 | event source object as the <parameter>source</parameter> | |
3144ebca | 115 | parameter.</para> |
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116 | </refsect1> |
117 | ||
118 | <refsect1> | |
119 | <title>Return Value</title> | |
120 | ||
121 | <para>On success, these functions return 0 or a positive | |
122 | integer. On failure, they return a negative errno-style error | |
f23e83b1 | 123 | code.</para> |
3144ebca | 124 | |
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125 | <refsect2> |
126 | <title>Errors</title> | |
3144ebca | 127 | |
b1de39de | 128 | <para>Returned errors may indicate the following problems:</para> |
3144ebca | 129 | |
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130 | <variablelist> |
131 | <varlistentry> | |
132 | <term><constant>-ENOMEM</constant></term> | |
3144ebca | 133 | |
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134 | <listitem><para>Not enough memory to allocate an object.</para></listitem> |
135 | </varlistentry> | |
3144ebca | 136 | |
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137 | <varlistentry> |
138 | <term><constant>-EINVAL</constant></term> | |
3144ebca | 139 | |
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140 | <listitem><para>An invalid argument has been passed.</para></listitem> |
141 | </varlistentry> | |
3144ebca | 142 | |
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143 | <varlistentry> |
144 | <term><constant>-EBUSY</constant></term> | |
3144ebca | 145 | |
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146 | <listitem><para>A handler is already installed for this |
147 | signal or the signal was not blocked previously.</para></listitem> | |
148 | </varlistentry> | |
3144ebca | 149 | |
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150 | <varlistentry> |
151 | <term><constant>-ESTALE</constant></term> | |
3144ebca | 152 | |
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153 | <listitem><para>The event loop is already terminated.</para></listitem> |
154 | </varlistentry> | |
3144ebca | 155 | |
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156 | <varlistentry> |
157 | <term><constant>-ECHILD</constant></term> | |
3144ebca | 158 | |
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159 | <listitem><para>The event loop has been created in a different process.</para></listitem> |
160 | </varlistentry> | |
3144ebca | 161 | |
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162 | <varlistentry> |
163 | <term><constant>-EDOM</constant></term> | |
3144ebca | 164 | |
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165 | <listitem><para>The passed event source is not a signal event source.</para></listitem> |
166 | </varlistentry> | |
3144ebca | 167 | |
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168 | </variablelist> |
169 | </refsect2> | |
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170 | </refsect1> |
171 | ||
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172 | <xi:include href="libsystemd-pkgconfig.xml" /> |
173 | ||
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174 | <refsect1> |
175 | <title>See Also</title> | |
176 | ||
177 | <para> | |
178 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
179 | <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
180 | <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
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181 | <citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
182 | <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
3144ebca | 183 | <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
edf25737 | 184 | <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
1eb54dc6 | 185 | <citerefentry><refentrytitle>sd_event_add_inotify</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
4dfefc19 | 186 | <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
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187 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
188 | <citerefentry><refentrytitle>sd_event_source_set_description</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
189 | <citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
190 | <citerefentry project='man-pages'><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry>, | |
191 | <citerefentry project='man-pages'><refentrytitle>signalfd</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
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192 | </para> |
193 | </refsect1> | |
194 | ||
195 | </refentry> |