diff options
Diffstat (limited to 'man/sd_event_add_child.xml')
| -rw-r--r-- | man/sd_event_add_child.xml | 223 |
1 files changed, 223 insertions, 0 deletions
diff --git a/man/sd_event_add_child.xml b/man/sd_event_add_child.xml new file mode 100644 index 0000000..c1b38f8 --- /dev/null +++ b/man/sd_event_add_child.xml @@ -0,0 +1,223 @@ +<?xml version='1.0'?> +<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" +"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> + +<!-- + SPDX-License-Identifier: LGPL-2.1+ +--> + +<refentry id="sd_event_add_child" xmlns:xi="http://www.w3.org/2001/XInclude"> + + <refentryinfo> + <title>sd_event_add_child</title> + <productname>systemd</productname> + </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="libsystemd-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_inotify</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> |