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<?xml version='1.0'?>
< !DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
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<!-- SPDX - License - Identifier: LGPL - 2.1 - or - later -->
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<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> .
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</para>
<xi:include href= "version-info.xml" xpointer= "v246" /> </listitem>
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</varlistentry>
<varlistentry >
<term > <constant > -ENOPKG</constant> </term>
<listitem > <para > Bus object <parameter > bus</parameter> could not be resolved.</para>
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<xi:include href= "version-info.xml" xpointer= "v246" />
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</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>
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<xi:include href= "version-info.xml" xpointer= "v246" />
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</listitem>
</varlistentry>
<varlistentry >
<term > <constant > -ECHILD</constant> </term>
<listitem > <para > The bus object <parameter > bus</parameter> was created in a different
process.</para>
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<xi:include href= "version-info.xml" xpointer= "v246" />
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</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" />
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<refsect1 >
<title > History</title>
<para > <function > sd_bus_start()</function> was added in version 246.</para>
</refsect1>
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<refsect1 >
<title > See Also</title>
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<para > <simplelist type= "inline" >
<member > <citerefentry > <refentrytitle > systemd</refentrytitle> <manvolnum > 1</manvolnum> </citerefentry> </member>
<member > <citerefentry > <refentrytitle > sd-bus</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> </member>
<member > <citerefentry > <refentrytitle > sd_bus_default</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> </member>
<member > <citerefentry > <refentrytitle > sd_bus_call_async</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> </member>
</simplelist> </para>
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</refsect1>
</refentry>