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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" |
681eb9cf FB |
3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [ |
4 | <!ENTITY % entities SYSTEM "custom-entities.ent" > | |
5 | %entities; | |
6 | ]> | |
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7 | |
8 | <!-- | |
5de0ccff | 9 | This file is part of systemd. |
edf25737 | 10 | |
5de0ccff | 11 | Copyright 2014 Zbigniew Jędrzejewski-Szmek |
edf25737 | 12 | |
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13 | systemd is free software; you can redistribute it and/or modify it |
14 | under the terms of the GNU Lesser General Public License as published by | |
15 | the Free Software Foundation; either version 2.1 of the License, or | |
16 | (at your option) any later version. | |
edf25737 | 17 | |
5de0ccff ZJS |
18 | systemd is distributed in the hope that it will be useful, but |
19 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
20 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
21 | Lesser General Public License for more details. | |
edf25737 | 22 | |
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23 | You should have received a copy of the GNU Lesser General Public License |
24 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
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25 | --> |
26 | ||
48f69d8f | 27 | <refentry id="sd_event_add_child"> |
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28 | |
29 | <refentryinfo> | |
30 | <title>sd_event_add_child</title> | |
31 | <productname>systemd</productname> | |
32 | ||
33 | <authorgroup> | |
34 | <author> | |
35 | <contrib>More text</contrib> | |
36 | <firstname>Zbigniew</firstname> | |
37 | <surname>Jędrzejewski-Szmek</surname> | |
38 | <email>zbyszek@in.waw.pl</email> | |
39 | </author> | |
40 | </authorgroup> | |
41 | </refentryinfo> | |
42 | ||
43 | <refmeta> | |
44 | <refentrytitle>sd_event_add_child</refentrytitle> | |
45 | <manvolnum>3</manvolnum> | |
46 | </refmeta> | |
47 | ||
48 | <refnamediv> | |
49 | <refname>sd_event_add_child</refname> | |
50 | <refname>sd_event_source_get_child_pid</refname> | |
51 | ||
52 | <refpurpose>Add a child state change event source to an event loop</refpurpose> | |
53 | </refnamediv> | |
54 | ||
55 | <refsynopsisdiv> | |
56 | <funcsynopsis> | |
57 | <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> | |
58 | ||
59 | <funcprototype> | |
60 | <funcdef>int <function>sd_event_add_child</function></funcdef> | |
61 | <paramdef>sd_event *<parameter>event</parameter></paramdef> | |
62 | <paramdef>sd_event_source **<parameter>source</parameter></paramdef> | |
63 | <paramdef>pid_t <parameter>pid</parameter></paramdef> | |
64 | <paramdef>int <parameter>options</parameter></paramdef> | |
65 | <paramdef>sd_event_child_handler_t <parameter>handler</parameter></paramdef> | |
66 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
67 | </funcprototype> | |
68 | ||
69 | <funcprototype> | |
70 | <funcdef>typedef int (*<function>sd_event_child_handler_t</function>)</funcdef> | |
71 | <paramdef>sd_event_source *<parameter>s</parameter></paramdef> | |
72 | <paramdef>const siginfo_t *<parameter>si</parameter></paramdef> | |
73 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
74 | </funcprototype> | |
75 | ||
76 | <funcprototype> | |
77 | <funcdef>int <function>sd_event_source_get_child_pid</function></funcdef> | |
78 | <paramdef>sd_event_source *<parameter>source</parameter></paramdef> | |
79 | <paramdef>pid_t *<parameter>pid</parameter></paramdef> | |
80 | </funcprototype> | |
81 | ||
82 | </funcsynopsis> | |
83 | </refsynopsisdiv> | |
84 | ||
85 | <refsect1> | |
86 | <title>Description</title> | |
87 | ||
88 | <para><function>sd_event_add_child()</function> adds a new child | |
89 | state change event source to an event loop object. The event loop | |
90 | is specified in <parameter>event</parameter>, the event source is | |
91 | returned in the <parameter>source</parameter> parameter. The | |
92 | <parameter>pid</parameter> parameter specifies the process to | |
93 | watch. The <parameter>handler</parameter> must reference a | |
94 | function to call when the process changes state. The handler | |
95 | function will be passed the <parameter>userdata</parameter> | |
96 | pointer, which may be chosen freely by the caller. The handler | |
97 | also receives a pointer to a <structname>const | |
98 | siginfo_t</structname> structure containing the information about | |
99 | the event. The <parameter>options</parameter> parameter determines | |
100 | which state changes will be watched for. It must contain an OR-ed | |
101 | mask of <constant>WEXITED</constant> (watch for the child | |
102 | terminating), <constant>WSTOPPED</constant> (watch for the child | |
103 | being stopped by a signal), and <constant>WCONTINUED</constant> | |
104 | (watch for the child being resumed by a signal). See | |
105 | <citerefentry><refentrytitle>waitid</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
922d948b | 106 | for further information.</para> |
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107 | |
108 | <para>Only a single handler may be installed for a specific | |
109 | child. The handler is enabled | |
110 | for a single event (<constant>SD_EVENT_ONESHOT</constant>), | |
111 | but this may be | |
112 | changed with | |
113 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>. | |
114 | If the handler function returns a negative error code, it will be | |
115 | disabled after the invocation, even if | |
116 | <constant>SD_EVENT_ON</constant> mode is set. | |
117 | </para> | |
118 | ||
119 | <para><function>sd_event_source_get_child_pid()</function> | |
120 | retrieves the configured <parameter>pid</parameter> of a child | |
121 | state change event source created previously with | |
122 | <function>sd_event_add_child()</function>. It takes the event | |
123 | source object as the <parameter>source</parameter> parameter and a | |
124 | pointer to <type>pid_t</type> to return the result in. | |
125 | </para> | |
126 | </refsect1> | |
127 | ||
128 | <refsect1> | |
129 | <title>Return Value</title> | |
130 | ||
131 | <para>On success, these functions return 0 or a positive | |
132 | integer. On failure, they return a negative errno-style error | |
133 | code.</para> | |
134 | </refsect1> | |
135 | ||
136 | <refsect1> | |
137 | <title>Errors</title> | |
138 | ||
139 | <para>Returned errors may indicate the following problems:</para> | |
140 | ||
141 | <variablelist> | |
142 | <varlistentry> | |
8474b70c | 143 | <term><constant>-ENOMEM</constant></term> |
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144 | |
145 | <listitem><para>Not enough memory to allocate an object.</para></listitem> | |
146 | </varlistentry> | |
147 | ||
148 | <varlistentry> | |
8474b70c | 149 | <term><constant>-EINVAL</constant></term> |
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150 | |
151 | <listitem><para>An invalid argument has been passed. This includes | |
cc98b302 | 152 | specifying an empty mask in <parameter>options</parameter> or a mask |
f131770b | 153 | which contains values different than a combination of |
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154 | <constant>WEXITED</constant>, <constant>WSTOPPED</constant>, and |
155 | <constant>WCONTINUED</constant>. | |
156 | </para></listitem> | |
157 | ||
158 | </varlistentry> | |
159 | ||
160 | <varlistentry> | |
8474b70c | 161 | <term><constant>-EBUSY</constant></term> |
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162 | |
163 | <listitem><para>An handler is already installed for this | |
164 | child.</para></listitem> | |
165 | ||
166 | </varlistentry> | |
167 | ||
168 | <varlistentry> | |
8474b70c | 169 | <term><constant>-ESTALE</constant></term> |
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170 | |
171 | <listitem><para>The event loop is already terminated.</para></listitem> | |
172 | ||
173 | </varlistentry> | |
174 | ||
175 | <varlistentry> | |
8474b70c | 176 | <term><constant>-ECHILD</constant></term> |
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177 | |
178 | <listitem><para>The event loop has been created in a different process.</para></listitem> | |
179 | ||
180 | </varlistentry> | |
181 | ||
182 | </variablelist> | |
183 | </refsect1> | |
184 | ||
185 | <refsect1> | |
186 | <title>Notes</title> | |
187 | ||
188 | <para><function>sd_event_add_child()</function> and the other functions | |
189 | described here are available as a shared library, which can be | |
190 | compiled and linked to with the | |
191 | <constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> | |
192 | file.</para> | |
193 | </refsect1> | |
194 | ||
195 | <refsect1> | |
196 | <title>See Also</title> | |
197 | ||
198 | <para> | |
199 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
200 | <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
201 | <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
202 | <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
203 | <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
4dfefc19 | 204 | <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
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205 | <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
206 | </para> | |
207 | </refsect1> | |
208 | ||
209 | </refentry> |