man/sd_bus_attach_event.xml

   1 <?xml version='1.0'?>
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4
   5 <!--
   6   SPDX-License-Identifier: LGPL-2.1+
   7 -->
   8
   9 <refentry id="sd_bus_attach_event"
  10           xmlns:xi="http://www.w3.org/2001/XInclude">
  11
  12   <refentryinfo>
  13     <title>sd_bus_attach_event</title>
  14     <productname>systemd</productname>
  15   </refentryinfo>
  16
  17   <refmeta>
  18     <refentrytitle>sd_bus_attach_event</refentrytitle>
  19     <manvolnum>3</manvolnum>
  20   </refmeta>
  21
  22   <refnamediv>
  23     <refname>sd_bus_attach_event</refname>
  24     <refname>sd_bus_detach_event</refname>
  25     <refname>sd_bus_get_event</refname>
  26
  27     <refpurpose>Attach a bus connection object to an event loop</refpurpose>
  28   </refnamediv>
  29
  30   <refsynopsisdiv>
  31     <funcsynopsis>
  32       <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
  33
  34       <funcprototype>
  35         <funcdef>int <function>sd_bus_attach_event</function></funcdef>
  36         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  37         <paramdef>sd_event *<parameter>e</parameter></paramdef>
  38         <paramdef>int <parameter>priority</parameter></paramdef>
  39       </funcprototype>
  40
  41       <funcprototype>
  42         <funcdef>int <function>sd_bus_detach_event</function></funcdef>
  43         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  44       </funcprototype>
  45
  46       <funcprototype>
  47         <funcdef>sd_event *<function>sd_bus_get_event</function></funcdef>
  48         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  49       </funcprototype>
  50     </funcsynopsis>
  51   </refsynopsisdiv>
  52
  53   <refsect1>
  54     <title>Description</title>
  55
  56     <para><function>sd_bus_attach_event()</function> attaches the specified bus connection object to an
  57     <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry> event loop object at
  58     the specified priority (see
  59     <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  60     for details on event loop priorities). When a bus connection object is attached to an event loop incoming messages
  61     will be automatically read and processed, and outgoing messages written, whenever the event loop is run. When the
  62     event loop is about to terminate, the bus connection is automatically flushed and closed (see
  63     <citerefentry><refentrytitle>sd_bus_set_close_on_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry> for
  64     details on this). By default bus connection objects are not attached to any event loop. When a bus connection
  65     object is attached to one it is not necessary to invoke
  66     <citerefentry><refentrytitle>sd_bus_wait</refentrytitle><manvolnum>3</manvolnum></citerefentry> or
  67     <citerefentry><refentrytitle>sd_bus_process</refentrytitle><manvolnum>3</manvolnum></citerefentry> as this
  68     functionality is handled automatically by the event loop.</para>
  69
  70     <para><function>sd_bus_detach_event()</function> detaches a bus object from its event loop.</para>
  71
  72     <para>The <function>sd_bus_get_event()</function> returns the event loop object the specified bus object is
  73     currently attached to, or <constant>NULL</constant> if it is currently not attached to any.</para>
  74
  75     <para>Note that <function>sd_bus_attach_event()</function> is only one of three supported ways to implement I/O
  76     event handling for bus connections. Alternatively use
  77     <citerefentry><refentrytitle>sd_bus_get_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry> for hooking up a
  78     bus connection object with external or manual event loops. Or use
  79     <citerefentry><refentrytitle>sd_bus_wait</refentrytitle><manvolnum>3</manvolnum></citerefentry> as a simple
  80     synchronous, blocking I/O waiting call.</para>
  81   </refsect1>
  82
  83   <refsect1>
  84     <title>Return Value</title>
  85
  86     <para>On success, <function>sd_bus_attach_event()</function> and <function>sd_bus_detach_event()</function> return
  87     0 or a positive integer. On failure, they return a negative errno-style error code.</para>
  88
  89     <para><function>sd_bus_get_event()</function> returns an event loop object or <constant>NULL</constant>.</para>
  90   </refsect1>
  91
  92   <refsect1>
  93     <title>Errors</title>
  94
  95     <para>Returned errors may indicate the following problems:</para>
  96
  97     <variablelist>
  98       <varlistentry>
  99         <term><constant>-ECHILD</constant></term>
 100
 101         <listitem><para>The bus connection has been created in a different process.</para></listitem>
 102       </varlistentry>
 103     </variablelist>
 104   </refsect1>
 105
 106   <xi:include href="libsystemd-pkgconfig.xml" />
 107
 108   <refsect1>
 109     <title>See Also</title>
 110
 111     <para>
 112       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 113       <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 114       <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 115       <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 116       <citerefentry><refentrytitle>sd_bus_set_close_on_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 117       <citerefentry><refentrytitle>sd_bus_wait</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 118       <citerefentry><refentrytitle>sd_bus_get_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 119     </para>
 120   </refsect1>
 121
 122 </refentry>