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f47781d8 | 1 | <?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*--> |
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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 | <!-- | |
52ad194e MB |
6 | SPDX-License-Identifier: LGPL-2.1+ |
7 | ||
e3bff60a | 8 | This file is part of systemd. |
5eef597e | 9 | |
e3bff60a | 10 | Copyright 2014 Zbigniew Jędrzejewski-Szmek |
5eef597e | 11 | |
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12 | systemd is free software; you can redistribute it and/or modify it |
13 | under the terms of the GNU Lesser General Public License as published by | |
14 | the Free Software Foundation; either version 2.1 of the License, or | |
15 | (at your option) any later version. | |
5eef597e | 16 | |
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17 | systemd is distributed in the hope that it will be useful, but |
18 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
20 | Lesser General Public License for more details. | |
5eef597e | 21 | |
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22 | You should have received a copy of the GNU Lesser General Public License |
23 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
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24 | --> |
25 | ||
4c89c718 | 26 | <refentry id="sd_event_get_fd" xmlns:xi="http://www.w3.org/2001/XInclude"> |
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27 | |
28 | <refentryinfo> | |
29 | <title>sd_event_get_fd</title> | |
30 | <productname>systemd</productname> | |
31 | ||
32 | <authorgroup> | |
33 | <author> | |
34 | <contrib>More text</contrib> | |
35 | <firstname>Zbigniew</firstname> | |
36 | <surname>Jędrzejewski-Szmek</surname> | |
37 | <email>zbyszek@in.waw.pl</email> | |
38 | </author> | |
39 | </authorgroup> | |
40 | </refentryinfo> | |
41 | ||
42 | <refmeta> | |
43 | <refentrytitle>sd_event_get_fd</refentrytitle> | |
44 | <manvolnum>3</manvolnum> | |
45 | </refmeta> | |
46 | ||
47 | <refnamediv> | |
48 | <refname>sd_event_get_fd</refname> | |
49 | ||
50 | <refpurpose>Obtain a file descriptor to poll for event loop events</refpurpose> | |
51 | </refnamediv> | |
52 | ||
53 | <refsynopsisdiv> | |
54 | <funcsynopsis> | |
4c89c718 | 55 | <funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo> |
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56 | |
57 | <funcprototype> | |
58 | <funcdef>int <function>sd_event_get_fd</function></funcdef> | |
4c89c718 | 59 | <paramdef>sd_event *<parameter>event</parameter></paramdef> |
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60 | </funcprototype> |
61 | ||
62 | </funcsynopsis> | |
63 | </refsynopsisdiv> | |
64 | ||
65 | <refsect1> | |
66 | <title>Description</title> | |
67 | ||
68 | <para><function>sd_event_get_fd()</function> returns the file | |
4c89c718 | 69 | descriptor that an event loop object returned by the |
5eef597e | 70 | <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
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71 | function uses to wait for events. This file descriptor may itself |
72 | be polled for | |
73 | <constant>POLLIN</constant>/<constant>EPOLLIN</constant> | |
74 | events. This makes it possible to embed an | |
5eef597e | 75 | <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
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76 | event loop into another, possibly foreign, event loop.</para> |
77 | ||
78 | <para>The returned file descriptor refers to an <citerefentry | |
79 | project='man-pages'><refentrytitle>epoll</refentrytitle><manvolnum>7</manvolnum></citerefentry> | |
80 | object. It is recommended not to alter it by invoking | |
81 | <citerefentry | |
82 | project='man-pages'><refentrytitle>epoll_ctl</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
83 | on it, in order to avoid interference with the event loop's inner | |
84 | logic and assumptions.</para> | |
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85 | </refsect1> |
86 | ||
87 | <refsect1> | |
88 | <title>Return Value</title> | |
89 | ||
90 | <para>On success, <function>sd_event_get_fd()</function> returns a | |
4c89c718 | 91 | non-negative file descriptor. On failure, it returns a negative |
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92 | errno-style error code.</para> |
93 | </refsect1> | |
94 | ||
95 | <refsect1> | |
96 | <title>Errors</title> | |
97 | ||
98 | <para>Returned errors may indicate the following problems:</para> | |
99 | ||
100 | <variablelist> | |
101 | <varlistentry> | |
102 | <term><constant>-EINVAL</constant></term> | |
103 | ||
104 | <listitem><para><parameter>event</parameter> is not a valid | |
105 | pointer to an <structname>sd_event</structname> structure. | |
106 | </para></listitem> | |
107 | </varlistentry> | |
108 | ||
109 | <varlistentry> | |
110 | <term><constant>-ECHILD</constant></term> | |
111 | ||
112 | <listitem><para>The event loop has been created in a different process.</para></listitem> | |
113 | ||
114 | </varlistentry> | |
115 | </variablelist> | |
116 | </refsect1> | |
117 | ||
118 | <refsect1> | |
119 | <title>Examples</title> | |
120 | ||
121 | <example> | |
4c89c718 | 122 | <title>Integration in the GLib event loop</title> |
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123 | |
124 | <programlisting><xi:include href="glib-event-glue.c" parse="text" /></programlisting> | |
125 | </example> | |
126 | </refsect1> | |
127 | ||
4c89c718 | 128 | <xi:include href="libsystemd-pkgconfig.xml" /> |
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129 | |
130 | <refsect1> | |
131 | <title>See Also</title> | |
132 | ||
133 | <para> | |
134 | <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
135 | <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
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136 | <citerefentry><refentrytitle>sd_event_wait</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
137 | <citerefentry project='man-pages'><refentrytitle>epoll_ctl</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
138 | <citerefentry project='man-pages'><refentrytitle>epoll</refentrytitle><manvolnum>7</manvolnum></citerefentry> | |
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139 | </para> |
140 | </refsect1> | |
141 | ||
142 | </refentry> |