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-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></listitem>
80        </varlistentry>
81
82        <varlistentry>
83          <term><constant>-ENOPKG</constant></term>
84
85          <listitem><para>Bus object <parameter>bus</parameter> could not be resolved.</para>
86          </listitem>
87        </varlistentry>
88
89        <varlistentry>
90          <term><constant>-EPERM</constant></term>
91
92          <listitem><para>The input parameter <parameter>bus</parameter> is in a wrong state
93          (<function>sd_bus_start()</function> may only be called once on a newly-created bus object).</para>
94          </listitem>
95        </varlistentry>
96
97        <varlistentry>
98          <term><constant>-ECHILD</constant></term>
99
100          <listitem><para>The bus object <parameter>bus</parameter> was created in a different
101          process.</para>
102          </listitem>
103        </varlistentry>
104      </variablelist>
105
106      <para>In addition, other connection-related errors may be returned. See
107      <citerefentry><refentrytitle>sd_bus_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
108    </refsect2>
109  </refsect1>
110
111  <xi:include href="libsystemd-pkgconfig.xml" />
112
113  <refsect1>
114    <title>See Also</title>
115
116    <para>
117      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
118      <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
119      <citerefentry><refentrytitle>sd_bus_default</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
120      <citerefentry><refentrytitle>sd_bus_call_async</refentrytitle><manvolnum>3</manvolnum></citerefentry>
121    </para>
122  </refsect1>
123
124</refentry>
125