--- /dev/null
+<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+
+<!--
+ This file is part of systemd.
+
+ Copyright 2014 Zbigniew Jędrzejewski-Szmek
+
+ systemd is free software; you can redistribute it and/or modify it
+ under the terms of the GNU Lesser General Public License as published by
+ the Free Software Foundation; either version 2.1 of the License, or
+ (at your option) any later version.
+
+ systemd is distributed in the hope that it will be useful, but
+ WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with systemd; If not, see <http://www.gnu.org/licenses/>.
+-->
+
+<refentry id="sd_event_add_child" xmlns:xi="http://www.w3.org/2001/XInclude">
+
+ <refentryinfo>
+ <title>sd_event_add_child</title>
+ <productname>systemd</productname>
+
+ <authorgroup>
+ <author>
+ <contrib>More text</contrib>
+ <firstname>Zbigniew</firstname>
+ <surname>Jędrzejewski-Szmek</surname>
+ <email>zbyszek@in.waw.pl</email>
+ </author>
+ </authorgroup>
+ </refentryinfo>
+
+ <refmeta>
+ <refentrytitle>sd_event_add_child</refentrytitle>
+ <manvolnum>3</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>sd_event_add_child</refname>
+ <refname>sd_event_source_get_child_pid</refname>
+ <refname>sd_event_child_handler_t</refname>
+
+ <refpurpose>Add a child process state change event source to an event loop</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+ <funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo>
+
+ <funcsynopsisinfo><token>typedef</token> struct sd_event_source sd_event_source;</funcsynopsisinfo>
+
+ <funcprototype>
+ <funcdef>typedef int (*<function>sd_event_child_handler_t</function>)</funcdef>
+ <paramdef>sd_event_source *<parameter>s</parameter></paramdef>
+ <paramdef>const siginfo_t *<parameter>si</parameter></paramdef>
+ <paramdef>void *<parameter>userdata</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_event_add_child</function></funcdef>
+ <paramdef>sd_event *<parameter>event</parameter></paramdef>
+ <paramdef>sd_event_source **<parameter>source</parameter></paramdef>
+ <paramdef>pid_t <parameter>pid</parameter></paramdef>
+ <paramdef>int <parameter>options</parameter></paramdef>
+ <paramdef>sd_event_child_handler_t <parameter>handler</parameter></paramdef>
+ <paramdef>void *<parameter>userdata</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_event_source_get_child_pid</function></funcdef>
+ <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
+ <paramdef>pid_t *<parameter>pid</parameter></paramdef>
+ </funcprototype>
+
+ </funcsynopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para><function>sd_event_add_child()</function> adds a new child
+ process state change event source to an event loop. The event loop
+ object is specified in the <parameter>event</parameter> parameter,
+ the event source object is returned in the
+ <parameter>source</parameter> parameter. The
+ <parameter>pid</parameter> parameter specifies the PID of the
+ process to watch. The <parameter>handler</parameter> must
+ reference a function to call when the process changes state. The
+ handler function will be passed the
+ <parameter>userdata</parameter> pointer, which may be chosen
+ freely by the caller. The handler also receives a pointer to a
+ <structname>siginfo_t</structname> structure containing
+ information about the child process event. The
+ <parameter>options</parameter> parameter determines which state
+ changes will be watched for. It must contain an OR-ed mask of
+ <constant>WEXITED</constant> (watch for the child process
+ terminating), <constant>WSTOPPED</constant> (watch for the child
+ process being stopped by a signal), and
+ <constant>WCONTINUED</constant> (watch for the child process being
+ resumed by a signal). See <citerefentry
+ project='man-pages'><refentrytitle>waitid</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+ for further information.</para>
+
+ <para>Only a single handler may be installed for a specific
+ child process. The handler is enabled for a single event
+ (<constant>SD_EVENT_ONESHOT</constant>), but this may be changed
+ with
+ <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
+ If the handler function returns a negative error code, it will be
+ disabled after the invocation, even if the
+ <constant>SD_EVENT_ON</constant> mode was requested before.
+ </para>
+
+ <para>To destroy an event source object use
+ <citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ but note that the event source is only removed from the event loop
+ when all references to the event source are dropped. To make sure
+ an event source does not fire anymore, even when there's still a
+ reference to it kept, consider setting the event source to
+ <constant>SD_EVENT_OFF</constant> with
+ <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
+
+ <para>If the second parameter of
+ <function>sd_event_add_child()</function> is passed as NULL no
+ reference to the event source object is returned. In this case the
+ event source is considered "floating", and will be destroyed
+ implicitly when the event loop itself is destroyed.</para>
+
+ <para>Note that the <parameter>handler</parameter> function is
+ invoked at a time where the child process is not reaped yet (and
+ thus still is exposed as a zombie process by the kernel). However,
+ the child will be reaped automatically after the function
+ returns. Child processes for which no child process state change
+ event sources are installed will not be reaped by the event loop
+ implementation.</para>
+
+ <para>If both a child process state change event source and a
+ <constant>SIGCHLD</constant> signal event source is installed in
+ the same event loop, the configured event source priorities decide
+ which event source is dispatched first. If the signal handler is
+ processed first, it should leave the child processes for which
+ child process state change event sources are installed unreaped.</para>
+
+ <para><function>sd_event_source_get_child_pid()</function>
+ retrieves the configured PID of a child process state change event
+ source created previously with
+ <function>sd_event_add_child()</function>. It takes the event
+ source object as the <parameter>source</parameter> parameter and a
+ pointer to a <type>pid_t</type> variable to return the process ID
+ in.
+ </para>
+ </refsect1>
+
+ <refsect1>
+ <title>Return Value</title>
+
+ <para>On success, these functions return 0 or a positive
+ integer. On failure, they return a negative errno-style error
+ code.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Errors</title>
+
+ <para>Returned errors may indicate the following problems:</para>
+
+ <variablelist>
+ <varlistentry>
+ <term><constant>-ENOMEM</constant></term>
+
+ <listitem><para>Not enough memory to allocate an object.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-EINVAL</constant></term>
+
+ <listitem><para>An invalid argument has been passed. This includes
+ specifying an empty mask in <parameter>options</parameter> or a mask
+ which contains values different than a combination of
+ <constant>WEXITED</constant>, <constant>WSTOPPED</constant>, and
+ <constant>WCONTINUED</constant>.
+ </para></listitem>
+
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-EBUSY</constant></term>
+
+ <listitem><para>A handler is already installed for this
+ child process.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-ESTALE</constant></term>
+
+ <listitem><para>The event loop is already terminated.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-ECHILD</constant></term>
+
+ <listitem><para>The event loop has been created in a different process.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>-EDOM</constant></term>
+
+ <listitem><para>The passed event source is not a child process event source.</para></listitem>
+ </varlistentry>
+
+ </variablelist>
+ </refsect1>
+
+ <xi:include href="libelogind-pkgconfig.xml" />
+
+ <refsect1>
+ <title>See Also</title>
+
+ <para>
+ <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_source_set_description</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry project='man-pages'><refentrytitle>waitid</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+ </para>
+ </refsect1>
+
+</refentry>
~ianmdlvl / elogind.git / blobdiff