man/sd_bus_attach_event.xml

   1 <?xml version='1.0'?>
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
   5
   6 <refentry id="sd_bus_attach_event"
   7           xmlns:xi="http://www.w3.org/2001/XInclude">
   8
   9   <refentryinfo>
  10     <title>sd_bus_attach_event</title>
  11     <productname>systemd</productname>
  12   </refentryinfo>
  13
  14   <refmeta>
  15     <refentrytitle>sd_bus_attach_event</refentrytitle>
  16     <manvolnum>3</manvolnum>
  17   </refmeta>
  18
  19   <refnamediv>
  20     <refname>sd_bus_attach_event</refname>
  21     <refname>sd_bus_detach_event</refname>
  22     <refname>sd_bus_get_event</refname>
  23
  24     <refpurpose>Attach a bus connection object to an event loop</refpurpose>
  25   </refnamediv>
  26
  27   <refsynopsisdiv>
  28     <funcsynopsis>
  29       <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
  30
  31       <funcprototype>
  32         <funcdef>int <function>sd_bus_attach_event</function></funcdef>
  33         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  34         <paramdef>sd_event *<parameter>e</parameter></paramdef>
  35         <paramdef>int <parameter>priority</parameter></paramdef>
  36       </funcprototype>
  37
  38       <funcprototype>
  39         <funcdef>int <function>sd_bus_detach_event</function></funcdef>
  40         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  41       </funcprototype>
  42
  43       <funcprototype>
  44         <funcdef>sd_event *<function>sd_bus_get_event</function></funcdef>
  45         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  46       </funcprototype>
  47     </funcsynopsis>
  48   </refsynopsisdiv>
  49
  50   <refsect1>
  51     <title>Description</title>
  52
  53     <para><function>sd_bus_attach_event()</function> attaches the specified bus connection object to an
  54     <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry> event loop object at
  55     the specified priority (see
  56     <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  57     for details on event loop priorities). When a bus connection object is attached to an event loop incoming messages
  58     will be automatically read and processed, and outgoing messages written, whenever the event loop is run. When the
  59     event loop is about to terminate, the bus connection is automatically flushed and closed (see
  60     <citerefentry><refentrytitle>sd_bus_set_close_on_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry> for
  61     details on this). By default bus connection objects are not attached to any event loop. When a bus connection
  62     object is attached to one it is not necessary to invoke
  63     <citerefentry><refentrytitle>sd_bus_wait</refentrytitle><manvolnum>3</manvolnum></citerefentry> or
  64     <citerefentry><refentrytitle>sd_bus_process</refentrytitle><manvolnum>3</manvolnum></citerefentry> as this
  65     functionality is handled automatically by the event loop.</para>
  66
  67     <para><function>sd_bus_detach_event()</function> detaches a bus object from its event loop.</para>
  68
  69     <para>The <function>sd_bus_get_event()</function> returns the event loop object the specified bus object is
  70     currently attached to, or <constant>NULL</constant> if it is currently not attached to any.</para>
  71
  72     <para>Note that <function>sd_bus_attach_event()</function> is only one of three supported ways to implement I/O
  73     event handling for bus connections. Alternatively use
  74     <citerefentry><refentrytitle>sd_bus_get_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry> for hooking up a
  75     bus connection object with external or manual event loops. Or use
  76     <citerefentry><refentrytitle>sd_bus_wait</refentrytitle><manvolnum>3</manvolnum></citerefentry> as a simple
  77     synchronous, blocking I/O waiting call.</para>
  78   </refsect1>
  79
  80   <refsect1>
  81     <title>Return Value</title>
  82
  83     <para>On success, <function>sd_bus_attach_event()</function> and <function>sd_bus_detach_event()</function> return
  84     0 or a positive integer. On failure, they return a negative errno-style error code.</para>
  85
  86     <para><function>sd_bus_get_event()</function> returns an event loop object or <constant>NULL</constant>.</para>
  87
  88     <refsect2>
  89       <title>Errors</title>
  90
  91       <para>Returned errors may indicate the following problems:</para>
  92
  93       <variablelist>
  94         <varlistentry>
  95           <term><constant>-ECHILD</constant></term>
  96
  97           <listitem><para>The bus connection has been created in a different process.</para></listitem>
  98         </varlistentry>
  99       </variablelist>
 100     </refsect2>
 101   </refsect1>
 102
 103   <xi:include href="libsystemd-pkgconfig.xml" />
 104
 105   <refsect1>
 106     <title>See Also</title>
 107
 108     <para>
 109       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 110       <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 111       <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 112       <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 113       <citerefentry><refentrytitle>sd_bus_set_close_on_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 114       <citerefentry><refentrytitle>sd_bus_wait</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 115       <citerefentry><refentrytitle>sd_bus_get_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 116     </para>
 117   </refsect1>
 118
 119 </refentry>