<?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"> <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> <refpurpose>Add a child state change event source to an event loop</refpurpose> </refnamediv> <refsynopsisdiv> <funcsynopsis> <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> <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>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_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 state change event source to an event loop object. The event loop is specified in <parameter>event</parameter>, the event source is returned in the <parameter>source</parameter> parameter. The <parameter>pid</parameter> parameter specifies 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>const siginfo_t</structname> structure containing the information about the 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 terminating), <constant>WSTOPPED</constant> (watch for the child being stopped by a signal), and <constant>WCONTINUED</constant> (watch for the child being resumed by a signal). See <citerefentry><refentrytitle>waitid</refentrytitle><manvolnum>2</manvolnum></citerefentry> for further information.</para> <para>Only a single handler may be installed for a specific child. 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 <constant>SD_EVENT_ON</constant> mode is set. </para> <para><function>sd_event_source_get_child_pid()</function> retrieves the configured <parameter>pid</parameter> of a child 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 <type>pid_t</type> to return the result 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>An handler is already installed for this child.</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> </variablelist> </refsect1> <refsect1> <title>Notes</title> <para><function>sd_event_add_child()</function> and the other functions described here are available as a shared library, which can be compiled and linked to with the <constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> file.</para> </refsect1> <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_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> </para> </refsect1> </refentry>