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3802a3d3 | 1 | <?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*--> |
edf25737 | 2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" |
12b42c76 | 3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
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4 | |
5 | <!-- | |
5de0ccff | 6 | This file is part of systemd. |
edf25737 | 7 | |
5de0ccff | 8 | Copyright 2014 Zbigniew Jędrzejewski-Szmek |
edf25737 | 9 | |
5de0ccff ZJS |
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. | |
edf25737 | 14 | |
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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. | |
edf25737 | 19 | |
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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/>. | |
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22 | --> |
23 | ||
48f69d8f | 24 | <refentry id="sd_event_add_child"> |
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25 | |
26 | <refentryinfo> | |
27 | <title>sd_event_add_child</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_child</refentrytitle> | |
42 | <manvolnum>3</manvolnum> | |
43 | </refmeta> | |
44 | ||
45 | <refnamediv> | |
46 | <refname>sd_event_add_child</refname> | |
47 | <refname>sd_event_source_get_child_pid</refname> | |
48 | ||
49 | <refpurpose>Add a child state change event source to an event loop</refpurpose> | |
50 | </refnamediv> | |
51 | ||
52 | <refsynopsisdiv> | |
53 | <funcsynopsis> | |
54 | <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> | |
55 | ||
56 | <funcprototype> | |
57 | <funcdef>int <function>sd_event_add_child</function></funcdef> | |
58 | <paramdef>sd_event *<parameter>event</parameter></paramdef> | |
59 | <paramdef>sd_event_source **<parameter>source</parameter></paramdef> | |
60 | <paramdef>pid_t <parameter>pid</parameter></paramdef> | |
61 | <paramdef>int <parameter>options</parameter></paramdef> | |
62 | <paramdef>sd_event_child_handler_t <parameter>handler</parameter></paramdef> | |
63 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
64 | </funcprototype> | |
65 | ||
66 | <funcprototype> | |
67 | <funcdef>typedef int (*<function>sd_event_child_handler_t</function>)</funcdef> | |
68 | <paramdef>sd_event_source *<parameter>s</parameter></paramdef> | |
69 | <paramdef>const siginfo_t *<parameter>si</parameter></paramdef> | |
70 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
71 | </funcprototype> | |
72 | ||
73 | <funcprototype> | |
74 | <funcdef>int <function>sd_event_source_get_child_pid</function></funcdef> | |
75 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
76 | <paramdef>pid_t *<parameter>pid</parameter></paramdef> | |
77 | </funcprototype> | |
78 | ||
79 | </funcsynopsis> | |
80 | </refsynopsisdiv> | |
81 | ||
82 | <refsect1> | |
83 | <title>Description</title> | |
84 | ||
85 | <para><function>sd_event_add_child()</function> adds a new child | |
86 | state change event source to an event loop object. The event loop | |
87 | is specified in <parameter>event</parameter>, the event source is | |
88 | returned in the <parameter>source</parameter> parameter. The | |
89 | <parameter>pid</parameter> parameter specifies the process to | |
90 | watch. The <parameter>handler</parameter> must reference a | |
91 | function to call when the process changes state. The handler | |
92 | function will be passed the <parameter>userdata</parameter> | |
93 | pointer, which may be chosen freely by the caller. The handler | |
94 | also receives a pointer to a <structname>const | |
95 | siginfo_t</structname> structure containing the information about | |
96 | the event. The <parameter>options</parameter> parameter determines | |
97 | which state changes will be watched for. It must contain an OR-ed | |
98 | mask of <constant>WEXITED</constant> (watch for the child | |
99 | terminating), <constant>WSTOPPED</constant> (watch for the child | |
100 | being stopped by a signal), and <constant>WCONTINUED</constant> | |
101 | (watch for the child being resumed by a signal). See | |
102 | <citerefentry><refentrytitle>waitid</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
922d948b | 103 | for further information.</para> |
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104 | |
105 | <para>Only a single handler may be installed for a specific | |
106 | child. The handler is enabled | |
107 | for a single event (<constant>SD_EVENT_ONESHOT</constant>), | |
108 | but this may be | |
109 | changed with | |
110 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>. | |
111 | If the handler function returns a negative error code, it will be | |
112 | disabled after the invocation, even if | |
113 | <constant>SD_EVENT_ON</constant> mode is set. | |
114 | </para> | |
115 | ||
116 | <para><function>sd_event_source_get_child_pid()</function> | |
117 | retrieves the configured <parameter>pid</parameter> of a child | |
118 | state change event source created previously with | |
119 | <function>sd_event_add_child()</function>. It takes the event | |
120 | source object as the <parameter>source</parameter> parameter and a | |
121 | pointer to <type>pid_t</type> to return the result in. | |
122 | </para> | |
123 | </refsect1> | |
124 | ||
125 | <refsect1> | |
126 | <title>Return Value</title> | |
127 | ||
128 | <para>On success, these functions return 0 or a positive | |
129 | integer. On failure, they return a negative errno-style error | |
130 | code.</para> | |
131 | </refsect1> | |
132 | ||
133 | <refsect1> | |
134 | <title>Errors</title> | |
135 | ||
136 | <para>Returned errors may indicate the following problems:</para> | |
137 | ||
138 | <variablelist> | |
139 | <varlistentry> | |
8474b70c | 140 | <term><constant>-ENOMEM</constant></term> |
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141 | |
142 | <listitem><para>Not enough memory to allocate an object.</para></listitem> | |
143 | </varlistentry> | |
144 | ||
145 | <varlistentry> | |
8474b70c | 146 | <term><constant>-EINVAL</constant></term> |
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147 | |
148 | <listitem><para>An invalid argument has been passed. This includes | |
cc98b302 | 149 | specifying an empty mask in <parameter>options</parameter> or a mask |
f131770b | 150 | which contains values different than a combination of |
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151 | <constant>WEXITED</constant>, <constant>WSTOPPED</constant>, and |
152 | <constant>WCONTINUED</constant>. | |
153 | </para></listitem> | |
154 | ||
155 | </varlistentry> | |
156 | ||
157 | <varlistentry> | |
8474b70c | 158 | <term><constant>-EBUSY</constant></term> |
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159 | |
160 | <listitem><para>An handler is already installed for this | |
161 | child.</para></listitem> | |
162 | ||
163 | </varlistentry> | |
164 | ||
165 | <varlistentry> | |
8474b70c | 166 | <term><constant>-ESTALE</constant></term> |
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167 | |
168 | <listitem><para>The event loop is already terminated.</para></listitem> | |
169 | ||
170 | </varlistentry> | |
171 | ||
172 | <varlistentry> | |
8474b70c | 173 | <term><constant>-ECHILD</constant></term> |
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174 | |
175 | <listitem><para>The event loop has been created in a different process.</para></listitem> | |
176 | ||
177 | </varlistentry> | |
178 | ||
179 | </variablelist> | |
180 | </refsect1> | |
181 | ||
182 | <refsect1> | |
183 | <title>Notes</title> | |
184 | ||
185 | <para><function>sd_event_add_child()</function> and the other functions | |
186 | described here are available as a shared library, which can be | |
187 | compiled and linked to with the | |
188 | <constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> | |
189 | file.</para> | |
190 | </refsect1> | |
191 | ||
192 | <refsect1> | |
193 | <title>See Also</title> | |
194 | ||
195 | <para> | |
196 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
197 | <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
198 | <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
199 | <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
200 | <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
4dfefc19 | 201 | <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
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202 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
203 | </para> | |
204 | </refsect1> | |
205 | ||
206 | </refentry> |