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<?xml version='1.0'?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
<refentry id="sd_bus_start"
xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>sd_bus_start</title>
<productname>systemd</productname>
</refentryinfo>
<refmeta>
<refentrytitle>sd_bus_start</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>sd_bus_start</refname>
<refpurpose>Initiate a bus connection to the D-bus broker daemon
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
<funcprototype>
<funcdef>int <function>sd_bus_start</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><function>sd_bus_start()</function> connects an existing bus connection object to the D-Bus
broker daemon, usually
<citerefentry project='die-net'><refentrytitle>dbus-daemon</refentrytitle><manvolnum>1</manvolnum></citerefentry>
or
<citerefentry project='mankier'><refentrytitle>dbus-broker</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
The mechanism to use for the connection must be configured before the call to
<function>sd_bus_start()</function>, using one of
<citerefentry><refentrytitle>sd_bus_set_address</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_set_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry>, or
<citerefentry><refentrytitle>sd_bus_set_exec</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
<function>sd_bus_start()</function> will open the connection socket or spawn the executable as
needed, and asynchronously start a <function>org.freedesktop.DBus.Hello()</function> call. The
answer to the Hello call will be processed later from
<citerefentry><refentrytitle>sd_bus_process</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If
opening of the connection or queuing of the asynchronous call fail, the connection will be closed with
<citerefentry><refentrytitle>sd_bus_close</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
<para>In most cases, it is better to use
<citerefentry><refentrytitle>sd_bus_default_user</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_default_system</refentrytitle><manvolnum>3</manvolnum></citerefentry>
or related calls instead of the more low-level <function>sd_bus_new()</function> and
<function>sd_bus_start()</function>. The higher-level functions not only allocate a bus object but also
start the connection to a well-known bus in a single function call.</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para>On success, this function returns a non-negative integer. On failure, it returns a negative
errno-style error code.</para>
<refsect2 id='errors'>
<title>Errors</title>
<variablelist>
<varlistentry>
<term><constant>-EINVAL</constant></term>
<listitem><para>The input parameter <parameter>bus</parameter> is <constant>NULL</constant>.
</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>-ENOPKG</constant></term>
<listitem><para>Bus object <parameter>bus</parameter> could not be resolved.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>-EPERM</constant></term>
<listitem><para>The input parameter <parameter>bus</parameter> is in a wrong state
(<function>sd_bus_start()</function> may only be called once on a newly-created bus object).</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>-ECHILD</constant></term>
<listitem><para>The bus object <parameter>bus</parameter> was created in a different
process.</para>
</listitem>
</varlistentry>
</variablelist>
<para>In addition, other connection-related errors may be returned. See
<citerefentry><refentrytitle>sd_bus_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
</refsect2>
</refsect1>
<xi:include href="libsystemd-pkgconfig.xml" />
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_default</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_call_async</refentrytitle><manvolnum>3</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
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