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3802a3d3 | 1 | <?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*--> |
ba4b3566 | 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 | <!-- | |
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6 | SPDX-License-Identifier: LGPL-2.1+ |
7 | ||
5de0ccff | 8 | This file is part of systemd. |
ba4b3566 | 9 | |
5de0ccff | 10 | Copyright 2014 Zbigniew Jędrzejewski-Szmek |
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11 | --> |
12 | ||
dc83f27a | 13 | <refentry id="sd_event_get_fd" xmlns:xi="http://www.w3.org/2001/XInclude"> |
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14 | |
15 | <refentryinfo> | |
16 | <title>sd_event_get_fd</title> | |
17 | <productname>systemd</productname> | |
18 | ||
19 | <authorgroup> | |
20 | <author> | |
21 | <contrib>More text</contrib> | |
22 | <firstname>Zbigniew</firstname> | |
23 | <surname>Jędrzejewski-Szmek</surname> | |
24 | <email>zbyszek@in.waw.pl</email> | |
25 | </author> | |
26 | </authorgroup> | |
27 | </refentryinfo> | |
28 | ||
29 | <refmeta> | |
30 | <refentrytitle>sd_event_get_fd</refentrytitle> | |
31 | <manvolnum>3</manvolnum> | |
32 | </refmeta> | |
33 | ||
34 | <refnamediv> | |
35 | <refname>sd_event_get_fd</refname> | |
36 | ||
37 | <refpurpose>Obtain a file descriptor to poll for event loop events</refpurpose> | |
38 | </refnamediv> | |
39 | ||
40 | <refsynopsisdiv> | |
41 | <funcsynopsis> | |
dc83f27a | 42 | <funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo> |
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43 | |
44 | <funcprototype> | |
45 | <funcdef>int <function>sd_event_get_fd</function></funcdef> | |
dc83f27a | 46 | <paramdef>sd_event *<parameter>event</parameter></paramdef> |
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47 | </funcprototype> |
48 | ||
49 | </funcsynopsis> | |
50 | </refsynopsisdiv> | |
51 | ||
52 | <refsect1> | |
53 | <title>Description</title> | |
54 | ||
55 | <para><function>sd_event_get_fd()</function> returns the file | |
dc83f27a | 56 | descriptor that an event loop object returned by the |
ba4b3566 | 57 | <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
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58 | function uses to wait for events. This file descriptor may itself |
59 | be polled for | |
60 | <constant>POLLIN</constant>/<constant>EPOLLIN</constant> | |
61 | events. This makes it possible to embed an | |
ba4b3566 | 62 | <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
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63 | event loop into another, possibly foreign, event loop.</para> |
64 | ||
65 | <para>The returned file descriptor refers to an <citerefentry | |
66 | project='man-pages'><refentrytitle>epoll</refentrytitle><manvolnum>7</manvolnum></citerefentry> | |
67 | object. It is recommended not to alter it by invoking | |
68 | <citerefentry | |
69 | project='man-pages'><refentrytitle>epoll_ctl</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
70 | on it, in order to avoid interference with the event loop's inner | |
71 | logic and assumptions.</para> | |
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72 | </refsect1> |
73 | ||
74 | <refsect1> | |
75 | <title>Return Value</title> | |
76 | ||
77 | <para>On success, <function>sd_event_get_fd()</function> returns a | |
dc83f27a | 78 | non-negative file descriptor. On failure, it returns a negative |
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79 | errno-style error code.</para> |
80 | </refsect1> | |
81 | ||
82 | <refsect1> | |
83 | <title>Errors</title> | |
84 | ||
85 | <para>Returned errors may indicate the following problems:</para> | |
86 | ||
87 | <variablelist> | |
88 | <varlistentry> | |
89 | <term><constant>-EINVAL</constant></term> | |
90 | ||
91 | <listitem><para><parameter>event</parameter> is not a valid | |
92 | pointer to an <structname>sd_event</structname> structure. | |
93 | </para></listitem> | |
94 | </varlistentry> | |
95 | ||
96 | <varlistentry> | |
97 | <term><constant>-ECHILD</constant></term> | |
98 | ||
99 | <listitem><para>The event loop has been created in a different process.</para></listitem> | |
100 | ||
101 | </varlistentry> | |
102 | </variablelist> | |
103 | </refsect1> | |
104 | ||
105 | <refsect1> | |
106 | <title>Examples</title> | |
107 | ||
108 | <example> | |
dc83f27a | 109 | <title>Integration in the GLib event loop</title> |
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110 | |
111 | <programlisting><xi:include href="glib-event-glue.c" parse="text" /></programlisting> | |
112 | </example> | |
113 | </refsect1> | |
114 | ||
dc83f27a | 115 | <xi:include href="libsystemd-pkgconfig.xml" /> |
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116 | |
117 | <refsect1> | |
118 | <title>See Also</title> | |
119 | ||
120 | <para> | |
121 | <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
122 | <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
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123 | <citerefentry><refentrytitle>sd_event_wait</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
124 | <citerefentry project='man-pages'><refentrytitle>epoll_ctl</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
125 | <citerefentry project='man-pages'><refentrytitle>epoll</refentrytitle><manvolnum>7</manvolnum></citerefentry> | |
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126 | </para> |
127 | </refsect1> | |
128 | ||
129 | </refentry> |