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| Copyright 2014 Zbigniew Jędrzejewski-Szmek |
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| |
| <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> |