<?xml version='1.0'?> <!--*-nxml-*--> <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> <!-- This file is part of systemd. Copyright 2014 Zbigniew Jędrzejewski-Szmek systemd is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. systemd is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with systemd; If not, see <http://www.gnu.org/licenses/>. --> <refentry id="sd_bus_open_user"> <refentryinfo> <title>sd_bus_open_user</title> <productname>systemd</productname> <authorgroup> <author> <contrib>A monkey with a typewriter</contrib> <firstname>Zbigniew</firstname> <surname>Jędrzejewski-Szmek</surname> <email>zbyszek@in.waw.pl</email> </author> </authorgroup> </refentryinfo> <refmeta> <refentrytitle>sd_bus_open_user</refentrytitle> <manvolnum>3</manvolnum> </refmeta> <refnamediv> <refname>sd_bus_open_user</refname> <refname>sd_bus_open_system</refname> <refname>sd_bus_open_system_remote</refname> <refname>sd_bus_open_system_container</refname> <refname>sd_bus_default_user</refname> <refname>sd_bus_default_system</refname> <refpurpose>Open a connection to the system or user bus</refpurpose> </refnamediv> <refsynopsisdiv> <funcsynopsis> <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> <funcprototype> <funcdef>int <function>sd_bus_open_user</function></funcdef> <paramdef>sd_bus** <parameter>bus</parameter></paramdef> </funcprototype> <funcprototype> <funcdef>int <function>sd_bus_open_system</function></funcdef> <paramdef>sd_bus** <parameter>bus</parameter></paramdef> </funcprototype> <funcprototype> <funcdef>int <function>sd_bus_open_system_remote</function></funcdef> <paramdef>const char *<parameter>host</parameter></paramdef> <paramdef>sd_bus** <parameter>bus</parameter></paramdef> </funcprototype> <funcprototype> <funcdef>int <function>sd_bus_open_system_container</function></funcdef> <paramdef>const char *<parameter>machine</parameter></paramdef> <paramdef>sd_bus** <parameter>bus</parameter></paramdef> </funcprototype> <funcprototype> <funcdef>int <function>sd_bus_default_user</function></funcdef> <paramdef>sd_bus** <parameter>bus</parameter></paramdef> </funcprototype> <funcprototype> <funcdef>int <function>sd_bus_default_system</function></funcdef> <paramdef>sd_bus** <parameter>bus</parameter></paramdef> </funcprototype> </funcsynopsis> </refsynopsisdiv> <refsect1> <title>Description</title> <para><function>sd_bus_open_user()</function> creates a new bus object and opens a connection to the the user bus. <function>sd_bus_open_system()</function> does the same, but connects to the system bus.</para> <para>If <varname>$DBUS_SESSION_BUS_ADDRESS</varname> environment variable is set (c.f. <citerefentry><refentrytitle>environ</refentrytitle><manvolnum>7</manvolnum></citerefentry>), it will be used as the address of the user bus. This variable can contain multiple addresses separated by <literal>;</literal>. If this variable is not set, a suitable default for the default user D-Bus instance will be used.</para> <para>If <varname>$DBUS_SYSTEM_BUS_ADDRESS</varname> environment variable is set, it will be used as the address of the system bus. This variable uses the same syntax as <varname>$DBUS_SESSION_BUS_ADDRESS</varname>/. If this variable is not set, a suitable default for the default system D-Bus instance will be used.</para> <para><function>sd_bus_open_system_remote()</function> connects to the system bus on the specified <parameter>host</parameter> using SSH. <parameter>host</parameter> consists of an optional user name followed by the <literal>@</literal> symbol, and the hostname. </para> <para><function>sd_bus_open_system_remote()</function> connects to the system bus in the specified <parameter>machine</parameter>, where <parameter>machine</parameter> is the name of a container. See <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry> for more information about "machines".</para> <para><function>sd_bus_default_user()</function> returns a bus object connected to the user bus. This bus object is shared per-thread. It is created on the first invocation of <function>sd_bus_default_user()</function>, and subsequent invocations returns a reference to the same object.</para> <para><function>sd_bus_default_system()</function> is similar to <function>sd_bus_default_user()</function>, but connects to the system bus.</para> </refsect1> <refsect1> <title>Return Value</title> <para>On success, these calls return 0 or a positive integer. On failure, these calls return a negative errno-style error code.</para> </refsect1> <refsect1> <title>Reference ownership</title> <para>Functions <function>sd_bus_open_user()</function>, <function>sd_bus_open_system()</function>, <function>sd_bus_open_system_remote()</function>, and <function>sd_bus_open_system_machine()</function> return a new object and the caller owns the sole reference. When not needed anymore, this reference should be destroyed with <citerefentry><refentrytitle>sd_bus_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>. </para> <para>Functions <function>sd_bus_default_user()</function> and <function>sd_bus_default_system()</function> do not create a new reference.</para> </refsect1> <refsect1> <title>Errors</title> <para>Returned errors may indicate the following problems:</para> <variablelist> <varlistentry> <term><varname>-EINVAL</varname></term> <listitem><para>Specified parameter is invalid (<constant>NULL</constant> in case of output parameters).</para></listitem> </varlistentry> <varlistentry> <term><varname>-ENOMEM</varname></term> <listitem><para>Memory allocation failed.</para></listitem> </varlistentry> <para>In addition, any further connection-related errors may be by returned. See <citerefentry><refentrytitle>sd_bus_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> </variablelist> </refsect1> <refsect1> <title>Notes</title> <para><function>sd_bus_open_user()</function> and other functions described here are available as a shared library, which can be compiled and linked to with the <constant>libsystemd</constant> <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> file.</para> </refsect1> <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_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>, <citerefentry><refentrytitle>sd_bus_ref</refentrytitle><manvolnum>3</manvolnum></citerefentry>, <citerefentry><refentrytitle>sd_bus_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>, <citerefentry><refentrytitle>ssh</refentrytitle><manvolnum>1</manvolnum></citerefentry>, <citerefentry><refentrytitle>systemd-machined.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry> </para> </refsect1> </refentry>