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+<?xml version='1.0'?>
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
+ "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
+
+<refentry id="sd_event_get_fd" xmlns:xi="http://www.w3.org/2001/XInclude">
+
+ <refentryinfo>
+ <title>sd_event_get_fd</title>
+ <productname>systemd</productname>
+ </refentryinfo>
+
+ <refmeta>
+ <refentrytitle>sd_event_get_fd</refentrytitle>
+ <manvolnum>3</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>sd_event_get_fd</refname>
+
+ <refpurpose>Obtain a file descriptor to poll for event loop events</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+ <funcsynopsisinfo>#include &lt;systemd/sd-event.h&gt;</funcsynopsisinfo>
+
+ <funcprototype>
+ <funcdef>int <function>sd_event_get_fd</function></funcdef>
+ <paramdef>sd_event *<parameter>event</parameter></paramdef>
+ </funcprototype>
+
+ </funcsynopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para><function>sd_event_get_fd()</function> returns the file
+ descriptor that an event loop object returned by the
+ <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ function uses to wait for events. This file descriptor may itself
+ be polled for
+ <constant>POLLIN</constant>/<constant>EPOLLIN</constant>
+ events. This makes it possible to embed an
+ <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ event loop into another, possibly foreign, event loop.</para>
+
+ <para>The returned file descriptor refers to an <citerefentry
+ project='man-pages'><refentrytitle>epoll</refentrytitle><manvolnum>7</manvolnum></citerefentry>
+ object. It is recommended not to alter it by invoking
+ <citerefentry
+ project='man-pages'><refentrytitle>epoll_ctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+ on it, in order to avoid interference with the event loop's inner
+ logic and assumptions.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Return Value</title>
+
+ <para>On success, <function>sd_event_get_fd()</function> returns a non-negative file descriptor. On
+ failure, it returns a negative errno-style error code.</para>
+
+ <refsect2>
+ <title>Errors</title>
+
+ <para>Returned errors may indicate the following problems:</para>
+
+ <variablelist>
+ <varlistentry>
+ <term><constant>-EINVAL</constant></term>
+
+ <listitem><para><parameter>event</parameter> is not a valid pointer to an
+ <structname>sd_event</structname> structure.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-ECHILD</constant></term>
+
+ <listitem><para>The event loop has been created in a different process.</para></listitem>
+
+ </varlistentry>
+ </variablelist>
+ </refsect2>
+ </refsect1>
+
+ <refsect1>
+ <title>Examples</title>
+
+ <example>
+ <title>Integration in the GLib event loop</title>
+
+ <programlisting><xi:include href="glib-event-glue.c" parse="text" /></programlisting>
+ </example>
+ </refsect1>
+
+ <xi:include href="libsystemd-pkgconfig.xml" />
+
+ <refsect1>
+ <title>See Also</title>
+
+ <para>
+ <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_wait</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry project='man-pages'><refentrytitle>epoll_ctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
+ <citerefentry project='man-pages'><refentrytitle>epoll</refentrytitle><manvolnum>7</manvolnum></citerefentry>
+ </para>
+ </refsect1>
+
+</refentry>