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514094f9 | 1 | <?xml version='1.0'?> |
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 | <!-- | |
572eb058 | 6 | SPDX-License-Identifier: LGPL-2.1+ |
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7 | --> |
8 | ||
dc83f27a | 9 | <refentry id="sd_event_get_fd" xmlns:xi="http://www.w3.org/2001/XInclude"> |
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10 | |
11 | <refentryinfo> | |
12 | <title>sd_event_get_fd</title> | |
13 | <productname>systemd</productname> | |
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14 | </refentryinfo> |
15 | ||
16 | <refmeta> | |
17 | <refentrytitle>sd_event_get_fd</refentrytitle> | |
18 | <manvolnum>3</manvolnum> | |
19 | </refmeta> | |
20 | ||
21 | <refnamediv> | |
22 | <refname>sd_event_get_fd</refname> | |
23 | ||
24 | <refpurpose>Obtain a file descriptor to poll for event loop events</refpurpose> | |
25 | </refnamediv> | |
26 | ||
27 | <refsynopsisdiv> | |
28 | <funcsynopsis> | |
dc83f27a | 29 | <funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo> |
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30 | |
31 | <funcprototype> | |
32 | <funcdef>int <function>sd_event_get_fd</function></funcdef> | |
dc83f27a | 33 | <paramdef>sd_event *<parameter>event</parameter></paramdef> |
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34 | </funcprototype> |
35 | ||
36 | </funcsynopsis> | |
37 | </refsynopsisdiv> | |
38 | ||
39 | <refsect1> | |
40 | <title>Description</title> | |
41 | ||
42 | <para><function>sd_event_get_fd()</function> returns the file | |
dc83f27a | 43 | descriptor that an event loop object returned by the |
ba4b3566 | 44 | <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
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45 | function uses to wait for events. This file descriptor may itself |
46 | be polled for | |
47 | <constant>POLLIN</constant>/<constant>EPOLLIN</constant> | |
48 | events. This makes it possible to embed an | |
ba4b3566 | 49 | <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
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50 | event loop into another, possibly foreign, event loop.</para> |
51 | ||
52 | <para>The returned file descriptor refers to an <citerefentry | |
53 | project='man-pages'><refentrytitle>epoll</refentrytitle><manvolnum>7</manvolnum></citerefentry> | |
54 | object. It is recommended not to alter it by invoking | |
55 | <citerefentry | |
56 | project='man-pages'><refentrytitle>epoll_ctl</refentrytitle><manvolnum>2</manvolnum></citerefentry> | |
57 | on it, in order to avoid interference with the event loop's inner | |
58 | logic and assumptions.</para> | |
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59 | </refsect1> |
60 | ||
61 | <refsect1> | |
62 | <title>Return Value</title> | |
63 | ||
64 | <para>On success, <function>sd_event_get_fd()</function> returns a | |
dc83f27a | 65 | non-negative file descriptor. On failure, it returns a negative |
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66 | errno-style error code.</para> |
67 | </refsect1> | |
68 | ||
69 | <refsect1> | |
70 | <title>Errors</title> | |
71 | ||
72 | <para>Returned errors may indicate the following problems:</para> | |
73 | ||
74 | <variablelist> | |
75 | <varlistentry> | |
76 | <term><constant>-EINVAL</constant></term> | |
77 | ||
78 | <listitem><para><parameter>event</parameter> is not a valid | |
79 | pointer to an <structname>sd_event</structname> structure. | |
80 | </para></listitem> | |
81 | </varlistentry> | |
82 | ||
83 | <varlistentry> | |
84 | <term><constant>-ECHILD</constant></term> | |
85 | ||
86 | <listitem><para>The event loop has been created in a different process.</para></listitem> | |
87 | ||
88 | </varlistentry> | |
89 | </variablelist> | |
90 | </refsect1> | |
91 | ||
92 | <refsect1> | |
93 | <title>Examples</title> | |
94 | ||
95 | <example> | |
dc83f27a | 96 | <title>Integration in the GLib event loop</title> |
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97 | |
98 | <programlisting><xi:include href="glib-event-glue.c" parse="text" /></programlisting> | |
99 | </example> | |
100 | </refsect1> | |
101 | ||
dc83f27a | 102 | <xi:include href="libsystemd-pkgconfig.xml" /> |
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103 | |
104 | <refsect1> | |
105 | <title>See Also</title> | |
106 | ||
107 | <para> | |
108 | <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
109 | <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
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110 | <citerefentry><refentrytitle>sd_event_wait</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
111 | <citerefentry project='man-pages'><refentrytitle>epoll_ctl</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
112 | <citerefentry project='man-pages'><refentrytitle>epoll</refentrytitle><manvolnum>7</manvolnum></citerefentry> | |
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113 | </para> |
114 | </refsect1> | |
115 | ||
116 | </refentry> |