man/sd_bus_start.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/4.5/docbookx.dtd">
   4 <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
   5
   6 <refentry id="sd_bus_start"
   7           xmlns:xi="http://www.w3.org/2001/XInclude">
   8
   9   <refentryinfo>
  10     <title>sd_bus_start</title>
  11     <productname>systemd</productname>
  12   </refentryinfo>
  13
  14   <refmeta>
  15     <refentrytitle>sd_bus_start</refentrytitle>
  16     <manvolnum>3</manvolnum>
  17   </refmeta>
  18
  19   <refnamediv>
  20     <refname>sd_bus_start</refname>
  21
  22     <refpurpose>Initiate a bus connection to the D-bus broker daemon
  23     </refpurpose>
  24   </refnamediv>
  25
  26   <refsynopsisdiv>
  27     <funcsynopsis>
  28       <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
  29
  30       <funcprototype>
  31         <funcdef>int <function>sd_bus_start</function></funcdef>
  32         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  33       </funcprototype>
  34     </funcsynopsis>
  35   </refsynopsisdiv>
  36
  37   <refsect1>
  38     <title>Description</title>
  39
  40     <para><function>sd_bus_start()</function> connects an existing bus connection object to the D-Bus
  41     broker daemon, usually
  42     <citerefentry project='die-net'><refentrytitle>dbus-daemon</refentrytitle><manvolnum>1</manvolnum></citerefentry>
  43     or
  44     <citerefentry project='mankier'><refentrytitle>dbus-broker</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
  45     The mechanism to use for the connection must be configured before the call to
  46     <function>sd_bus_start()</function>, using one of
  47     <citerefentry><refentrytitle>sd_bus_set_address</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  48     <citerefentry><refentrytitle>sd_bus_set_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry>, or
  49     <citerefentry><refentrytitle>sd_bus_set_exec</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
  50     <function>sd_bus_start()</function> will open the connection socket or spawn the executable as
  51     needed, and asynchronously start a <function>org.freedesktop.DBus.Hello()</function> call. The
  52     answer to the Hello call will be processed later from
  53     <citerefentry><refentrytitle>sd_bus_process</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If
  54     opening of the connection or queuing of the asynchronous call fail, the connection will be closed with
  55     <citerefentry><refentrytitle>sd_bus_close</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
  56
  57     <para>In most cases, it is better to use
  58     <citerefentry><refentrytitle>sd_bus_default_user</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  59     <citerefentry><refentrytitle>sd_bus_default_system</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  60     or related calls instead of the more low-level <function>sd_bus_new()</function> and
  61     <function>sd_bus_start()</function>. The higher-level functions not only allocate a bus object but also
  62     start the connection to a well-known bus in a single function call.</para>
  63   </refsect1>
  64
  65   <refsect1>
  66     <title>Return Value</title>
  67
  68     <para>On success, this function returns a non-negative integer. On failure, it returns a negative
  69     errno-style error code.</para>
  70
  71     <refsect2 id='errors'>
  72       <title>Errors</title>
  73
  74       <variablelist>
  75         <varlistentry>
  76           <term><constant>-EINVAL</constant></term>
  77
  78           <listitem><para>The input parameter <parameter>bus</parameter> is <constant>NULL</constant>.
  79           </para>
  80
  81           <xi:include href="version-info.xml" xpointer="v246"/></listitem>
  82         </varlistentry>
  83
  84         <varlistentry>
  85           <term><constant>-ENOPKG</constant></term>
  86
  87           <listitem><para>Bus object <parameter>bus</parameter> could not be resolved.</para>
  88
  89           <xi:include href="version-info.xml" xpointer="v246"/>
  90           </listitem>
  91         </varlistentry>
  92
  93         <varlistentry>
  94           <term><constant>-EPERM</constant></term>
  95
  96           <listitem><para>The input parameter <parameter>bus</parameter> is in a wrong state
  97           (<function>sd_bus_start()</function> may only be called once on a newly-created bus object).</para>
  98
  99           <xi:include href="version-info.xml" xpointer="v246"/>
 100           </listitem>
 101         </varlistentry>
 102
 103         <varlistentry>
 104           <term><constant>-ECHILD</constant></term>
 105
 106           <listitem><para>The bus object <parameter>bus</parameter> was created in a different
 107           process.</para>
 108
 109           <xi:include href="version-info.xml" xpointer="v246"/>
 110           </listitem>
 111         </varlistentry>
 112       </variablelist>
 113
 114       <para>In addition, other connection-related errors may be returned. See
 115       <citerefentry><refentrytitle>sd_bus_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
 116     </refsect2>
 117   </refsect1>
 118
 119   <xi:include href="libsystemd-pkgconfig.xml" />
 120
 121   <refsect1>
 122     <title>History</title>
 123     <para><function>sd_bus_start()</function> was added in version 246.</para>
 124   </refsect1>
 125
 126   <refsect1>
 127     <title>See Also</title>
 128
 129     <para><simplelist type="inline">
 130       <member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
 131       <member><citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
 132       <member><citerefentry><refentrytitle>sd_bus_default</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
 133       <member><citerefentry><refentrytitle>sd_bus_call_async</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
 134     </simplelist></para>
 135   </refsect1>
 136
 137 </refentry>