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11a1589223
Files which are installed as-is (any .service and other unit files, .conf files, .policy files, etc), are left as is. My assumption is that SPDX identifiers are not yet that well known, so it's better to retain the extended header to avoid any doubt. I also kept any copyright lines. We can probably remove them, but it'd nice to obtain explicit acks from all involved authors before doing that.
236 lines
9.8 KiB
XML
236 lines
9.8 KiB
XML
<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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SPDX-License-Identifier: LGPL-2.1+
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This file is part of systemd.
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Copyright 2014 Zbigniew Jędrzejewski-Szmek
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-->
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<refentry id="sd_event_add_child" xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>sd_event_add_child</title>
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<productname>systemd</productname>
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<authorgroup>
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<author>
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<contrib>More text</contrib>
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<firstname>Zbigniew</firstname>
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<surname>Jędrzejewski-Szmek</surname>
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<email>zbyszek@in.waw.pl</email>
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</author>
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</authorgroup>
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</refentryinfo>
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<refmeta>
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<refentrytitle>sd_event_add_child</refentrytitle>
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<manvolnum>3</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>sd_event_add_child</refname>
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<refname>sd_event_source_get_child_pid</refname>
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<refname>sd_event_child_handler_t</refname>
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<refpurpose>Add a child process state change event source to an event loop</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo>
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<funcsynopsisinfo><token>typedef</token> struct sd_event_source sd_event_source;</funcsynopsisinfo>
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<funcprototype>
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<funcdef>typedef int (*<function>sd_event_child_handler_t</function>)</funcdef>
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<paramdef>sd_event_source *<parameter>s</parameter></paramdef>
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<paramdef>const siginfo_t *<parameter>si</parameter></paramdef>
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<paramdef>void *<parameter>userdata</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_event_add_child</function></funcdef>
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<paramdef>sd_event *<parameter>event</parameter></paramdef>
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<paramdef>sd_event_source **<parameter>source</parameter></paramdef>
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<paramdef>pid_t <parameter>pid</parameter></paramdef>
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<paramdef>int <parameter>options</parameter></paramdef>
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<paramdef>sd_event_child_handler_t <parameter>handler</parameter></paramdef>
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<paramdef>void *<parameter>userdata</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_event_source_get_child_pid</function></funcdef>
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<paramdef>sd_event_source *<parameter>source</parameter></paramdef>
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<paramdef>pid_t *<parameter>pid</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><function>sd_event_add_child()</function> adds a new child
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process state change event source to an event loop. The event loop
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object is specified in the <parameter>event</parameter> parameter,
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the event source object is returned in the
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<parameter>source</parameter> parameter. The
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<parameter>pid</parameter> parameter specifies the PID of the
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process to watch. The <parameter>handler</parameter> must
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reference a function to call when the process changes state. The
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handler function will be passed the
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<parameter>userdata</parameter> pointer, which may be chosen
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freely by the caller. The handler also receives a pointer to a
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<structname>siginfo_t</structname> structure containing
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information about the child process event. The
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<parameter>options</parameter> parameter determines which state
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changes will be watched for. It must contain an OR-ed mask of
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<constant>WEXITED</constant> (watch for the child process
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terminating), <constant>WSTOPPED</constant> (watch for the child
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process being stopped by a signal), and
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<constant>WCONTINUED</constant> (watch for the child process being
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resumed by a signal). See <citerefentry
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project='man-pages'><refentrytitle>waitid</refentrytitle><manvolnum>2</manvolnum></citerefentry>
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for further information.</para>
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<para>Only a single handler may be installed for a specific
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child process. The handler is enabled for a single event
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(<constant>SD_EVENT_ONESHOT</constant>), but this may be changed
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with
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<citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
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If the handler function returns a negative error code, it will be
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disabled after the invocation, even if the
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<constant>SD_EVENT_ON</constant> mode was requested before.
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</para>
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<para>To destroy an event source object use
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<citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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but note that the event source is only removed from the event loop
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when all references to the event source are dropped. To make sure
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an event source does not fire anymore, even when there's still a
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reference to it kept, consider setting the event source to
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<constant>SD_EVENT_OFF</constant> with
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<citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
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<para>If the second parameter of
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<function>sd_event_add_child()</function> is passed as NULL no
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reference to the event source object is returned. In this case the
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event source is considered "floating", and will be destroyed
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implicitly when the event loop itself is destroyed.</para>
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<para>Note that the <parameter>handler</parameter> function is
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invoked at a time where the child process is not reaped yet (and
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thus still is exposed as a zombie process by the kernel). However,
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the child will be reaped automatically after the function
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returns. Child processes for which no child process state change
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event sources are installed will not be reaped by the event loop
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implementation.</para>
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<para>If both a child process state change event source and a
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<constant>SIGCHLD</constant> signal event source is installed in
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the same event loop, the configured event source priorities decide
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which event source is dispatched first. If the signal handler is
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processed first, it should leave the child processes for which
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child process state change event sources are installed unreaped.</para>
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<para><function>sd_event_source_get_child_pid()</function>
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retrieves the configured PID of a child process state change event
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source created previously with
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<function>sd_event_add_child()</function>. It takes the event
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source object as the <parameter>source</parameter> parameter and a
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pointer to a <type>pid_t</type> variable to return the process ID
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in.
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</para>
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</refsect1>
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<refsect1>
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<title>Return Value</title>
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<para>On success, these functions return 0 or a positive
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integer. On failure, they return a negative errno-style error
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code.</para>
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</refsect1>
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<refsect1>
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<title>Errors</title>
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<para>Returned errors may indicate the following problems:</para>
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<variablelist>
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<varlistentry>
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<term><constant>-ENOMEM</constant></term>
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<listitem><para>Not enough memory to allocate an object.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-EINVAL</constant></term>
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<listitem><para>An invalid argument has been passed. This includes
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specifying an empty mask in <parameter>options</parameter> or a mask
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which contains values different than a combination of
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<constant>WEXITED</constant>, <constant>WSTOPPED</constant>, and
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<constant>WCONTINUED</constant>.
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</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-EBUSY</constant></term>
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<listitem><para>A handler is already installed for this
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child process.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-ESTALE</constant></term>
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<listitem><para>The event loop is already terminated.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-ECHILD</constant></term>
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<listitem><para>The event loop has been created in a different process.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-EDOM</constant></term>
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<listitem><para>The passed event source is not a child process event source.</para></listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<xi:include href="libsystemd-pkgconfig.xml" />
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_source_set_description</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><refentrytitle>waitid</refentrytitle><manvolnum>2</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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