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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"> | |
4 | ||
5 | <!-- | |
6 | This file is part of systemd. | |
7 | ||
8 | Copyright 2014 Zbigniew Jędrzejewski-Szmek | |
9 | ||
10 | systemd is free software; you can redistribute it and/or modify it | |
11 | under the terms of the GNU Lesser General Public License as published by | |
12 | the Free Software Foundation; either version 2.1 of the License, or | |
13 | (at your option) any later version. | |
14 | ||
15 | systemd is distributed in the hope that it will be useful, but | |
16 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
17 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
18 | Lesser General Public License for more details. | |
19 | ||
20 | You should have received a copy of the GNU Lesser General Public License | |
21 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
22 | --> | |
23 | ||
24 | <refentry id="sd_event_add_signal" xmlns:xi="http://www.w3.org/2001/XInclude"> | |
25 | ||
26 | <refentryinfo> | |
27 | <title>sd_event_add_signal</title> | |
28 | <productname>systemd</productname> | |
29 | ||
30 | <authorgroup> | |
31 | <author> | |
32 | <contrib>More text</contrib> | |
33 | <firstname>Zbigniew</firstname> | |
34 | <surname>Jędrzejewski-Szmek</surname> | |
35 | <email>zbyszek@in.waw.pl</email> | |
36 | </author> | |
37 | </authorgroup> | |
38 | </refentryinfo> | |
39 | ||
40 | <refmeta> | |
41 | <refentrytitle>sd_event_add_signal</refentrytitle> | |
42 | <manvolnum>3</manvolnum> | |
43 | </refmeta> | |
44 | ||
45 | <refnamediv> | |
46 | <refname>sd_event_add_signal</refname> | |
47 | <refname>sd_event_source_get_signal</refname> | |
48 | <refname>sd_event_signal_handler_t</refname> | |
49 | ||
50 | <refpurpose>Add a UNIX process signal event source to an event | |
51 | loop</refpurpose> | |
52 | </refnamediv> | |
53 | ||
54 | <refsynopsisdiv> | |
55 | <funcsynopsis> | |
56 | <funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo> | |
57 | ||
58 | <funcsynopsisinfo><token>typedef</token> struct sd_event_source sd_event_source;</funcsynopsisinfo> | |
59 | ||
60 | <funcprototype> | |
61 | <funcdef>typedef int (*<function>sd_event_signal_handler_t</function>)</funcdef> | |
62 | <paramdef>sd_event_source *<parameter>s</parameter></paramdef> | |
63 | <paramdef>const struct signalfd_siginfo *<parameter>si</parameter></paramdef> | |
64 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
65 | </funcprototype> | |
66 | ||
67 | <funcprototype> | |
68 | <funcdef>int <function>sd_event_add_signal</function></funcdef> | |
69 | <paramdef>sd_event *<parameter>event</parameter></paramdef> | |
70 | <paramdef>sd_event_source **<parameter>source</parameter></paramdef> | |
71 | <paramdef>int <parameter>signal</parameter></paramdef> | |
72 | <paramdef>sd_event_signal_handler_t <parameter>handler</parameter></paramdef> | |
73 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
74 | </funcprototype> | |
75 | ||
76 | <funcprototype> | |
77 | <funcdef>int <function>sd_event_source_get_signal</function></funcdef> | |
78 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
79 | </funcprototype> | |
80 | ||
81 | </funcsynopsis> | |
82 | </refsynopsisdiv> | |
83 | ||
84 | <refsect1> | |
85 | <title>Description</title> | |
86 | ||
87 | <para><function>sd_event_add_signal()</function> adds a new UNIX | |
88 | process signal event source to an event loop. The event loop | |
89 | object is specified in the <parameter>event</parameter> parameter, | |
90 | and the event source object is returned in the | |
91 | <parameter>source</parameter> parameter. The | |
92 | <parameter>signal</parameter> parameter specifies the numeric | |
93 | signal to be handled (see <citerefentry | |
94 | project='man-pages'><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry>). | |
95 | The <parameter>handler</parameter> parameter must reference a | |
96 | function to call when the signal is received or be | |
97 | <constant>NULL</constant>. The handler function will be passed | |
98 | the <parameter>userdata</parameter> pointer, which may be chosen | |
99 | freely by the caller. The handler also receives a pointer to a | |
100 | <structname>signalfd_siginfo</structname> structure containing | |
101 | information about the received signal. See <citerefentry | |
102 | project='man-pages'><refentrytitle>signalfd</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
103 | for further information.</para> | |
104 | ||
105 | <para>Only a single handler may be installed for a specific | |
106 | signal. The signal will be unblocked by this call, and must be | |
107 | blocked before this function is called in all threads (using | |
108 | <citerefentry | |
109 | project='man-pages'><refentrytitle>sigprocmask</refentrytitle><manvolnum>2</manvolnum></citerefentry>). If | |
110 | the handler is not specified (<parameter>handler</parameter> is | |
111 | <constant>NULL</constant>), a default handler which causes the | |
112 | program to exit cleanly will be used.</para> | |
113 | ||
114 | <para>By default, the event source is enabled permanently | |
115 | (<constant>SD_EVENT_ON</constant>), but this may be changed with | |
116 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>. | |
117 | If the handler function returns a negative error code, it will be | |
118 | disabled after the invocation, even if the | |
119 | <constant>SD_EVENT_ON</constant> mode was requested before. | |
120 | </para> | |
121 | ||
122 | <para>To destroy an event source object use | |
123 | <citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
124 | but note that the event source is only removed from the event loop | |
125 | when all references to the event source are dropped. To make sure | |
126 | an event source does not fire anymore, even if it is still referenced, | |
127 | disable the event source using | |
128 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
129 | with <constant>SD_EVENT_OFF</constant>.</para> | |
130 | ||
131 | <para>If the second parameter of | |
132 | <function>sd_event_add_signal()</function> is | |
133 | <constant>NULL</constant> no reference to the event source object | |
134 | is returned. In this case the event source is considered | |
135 | "floating", and will be destroyed implicitly when the event loop | |
136 | itself is destroyed.</para> | |
137 | ||
138 | <para><function>sd_event_source_get_signal()</function> returns | |
139 | the configured signal number of an event source created previously | |
140 | with <function>sd_event_add_signal()</function>. It takes the | |
141 | event source object as the <parameter>source</parameter> | |
142 | parameter.</para> | |
143 | </refsect1> | |
144 | ||
145 | <refsect1> | |
146 | <title>Return Value</title> | |
147 | ||
148 | <para>On success, these functions return 0 or a positive | |
149 | integer. On failure, they return a negative errno-style error | |
150 | code.</para> | |
151 | </refsect1> | |
152 | ||
153 | <refsect1> | |
154 | <title>Errors</title> | |
155 | ||
156 | <para>Returned errors may indicate the following problems:</para> | |
157 | ||
158 | <variablelist> | |
159 | <varlistentry> | |
160 | <term><constant>-ENOMEM</constant></term> | |
161 | ||
162 | <listitem><para>Not enough memory to allocate an object.</para></listitem> | |
163 | </varlistentry> | |
164 | ||
165 | <varlistentry> | |
166 | <term><constant>-EINVAL</constant></term> | |
167 | ||
168 | <listitem><para>An invalid argument has been passed.</para></listitem> | |
169 | </varlistentry> | |
170 | ||
171 | <varlistentry> | |
172 | <term><constant>-EBUSY</constant></term> | |
173 | ||
174 | <listitem><para>A handler is already installed for this | |
175 | signal or the signal was not blocked previously.</para></listitem> | |
176 | </varlistentry> | |
177 | ||
178 | <varlistentry> | |
179 | <term><constant>-ESTALE</constant></term> | |
180 | ||
181 | <listitem><para>The event loop is already terminated.</para></listitem> | |
182 | </varlistentry> | |
183 | ||
184 | <varlistentry> | |
185 | <term><constant>-ECHILD</constant></term> | |
186 | ||
187 | <listitem><para>The event loop has been created in a different process.</para></listitem> | |
188 | </varlistentry> | |
189 | ||
190 | <varlistentry> | |
191 | <term><constant>-EDOM</constant></term> | |
192 | ||
193 | <listitem><para>The passed event source is not a signal event source.</para></listitem> | |
194 | </varlistentry> | |
195 | ||
196 | </variablelist> | |
197 | </refsect1> | |
198 | ||
199 | <xi:include href="libsystemd-pkgconfig.xml" /> | |
200 | ||
201 | <refsect1> | |
202 | <title>See Also</title> | |
203 | ||
204 | <para> | |
205 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
206 | <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
207 | <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
208 | <citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
209 | <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
210 | <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
211 | <citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
212 | <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
213 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
214 | <citerefentry><refentrytitle>sd_event_source_set_description</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
215 | <citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
216 | <citerefentry project='man-pages'><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry>, | |
217 | <citerefentry project='man-pages'><refentrytitle>signalfd</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
218 | </para> | |
219 | </refsect1> | |
220 | ||
221 | </refentry> |