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<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>sd_bus_open_user</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><style>
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<a href="../libudev/index.html">gudev </a><span style="float:right">systemd 215</span><hr><div class="refentry"><a name="sd_bus_open_user"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>sd_bus_open_user, sd_bus_open_system, sd_bus_open_system_remote, sd_bus_open_system_container, sd_bus_default_user, sd_bus_default_system — Open a connection to the system or user bus</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="funcsynopsis"><pre class="funcsynopsisinfo">#include <systemd/sd-bus.h></pre><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_bus_open_user</b>(</code></td><td>sd_bus **<var class="pdparam">bus</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_bus_open_system</b>(</code></td><td>sd_bus **<var class="pdparam">bus</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_bus_open_system_remote</b>(</code></td><td>const char *<var class="pdparam">host</var>, </td></tr><tr><td> </td><td>sd_bus **<var class="pdparam">bus</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_bus_open_system_container</b>(</code></td><td>const char *<var class="pdparam">machine</var>, </td></tr><tr><td> </td><td>sd_bus **<var class="pdparam">bus</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_bus_default_user</b>(</code></td><td>sd_bus **<var class="pdparam">bus</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_bus_default_system</b>(</code></td><td>sd_bus **<var class="pdparam">bus</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1"><a name="idm214201032336"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description">¶</a></h2><p><code class="function">sd_bus_open_user()</code> creates a new bus
object and opens a connection to the user bus.
<code class="function">sd_bus_open_system()</code> does the same, but
connects to the system bus.</p><p>If the <code class="varname">$DBUS_SESSION_BUS_ADDRESS</code> environment
variable is set
(cf. <a href="environ.html"><span class="citerefentry"><span class="refentrytitle">environ</span>(7)</span></a>),
it will be used as the address of the user bus. This variable can
contain multiple addresses separated by "<code class="literal">;</code>". If
this variable is not set, a suitable default for the default user
D-Bus instance will be used.</p><p>If the <code class="varname">$DBUS_SYSTEM_BUS_ADDRESS</code> environment
variable is set, it will be used as the address of the system
bus. This variable uses the same syntax as
<code class="varname">$DBUS_SESSION_BUS_ADDRESS</code>/. If this variable is
not set, a suitable default for the default system D-Bus instance
will be used.</p><p><code class="function">sd_bus_open_system_remote()</code> connects to
the system bus on the specified <em class="parameter"><code>host</code></em> using
SSH. <em class="parameter"><code>host</code></em> consists of an optional user name
followed by the "<code class="literal">@</code>" symbol, and the hostname.
</p><p><code class="function">sd_bus_open_system_remote()</code> connects to
the system bus in the specified <em class="parameter"><code>machine</code></em>,
where <em class="parameter"><code>machine</code></em> is the name of a container.
See
<a href="machinectl.html"><span class="citerefentry"><span class="refentrytitle">machinectl</span>(1)</span></a>
for more information about "machines".</p><p><code class="function">sd_bus_default_user()</code> returns a bus
object connected to the user bus. Each thread has its own object, but it
may be passed around. It is created on the first invocation of
<code class="function">sd_bus_default_user()</code>, and subsequent
invocations returns a reference to the same object.</p><p><code class="function">sd_bus_default_system()</code> is similar to
<code class="function">sd_bus_default_user()</code>, but connects to the
system bus.</p></div><div class="refsect1"><a name="idm214201008656"></a><h2 id="Return Value">Return Value<a class="headerlink" title="Permalink to this headline" href="#Return%20Value">¶</a></h2><p>On success, these calls return 0 or a positive
integer. On failure, these calls return a negative
errno-style error code.</p></div><div class="refsect1"><a name="idm214201007328"></a><h2 id="Reference ownership">Reference ownership<a class="headerlink" title="Permalink to this headline" href="#Reference%20ownership">¶</a></h2><p>Functions <code class="function">sd_bus_open_user()</code>,
<code class="function">sd_bus_open_system()</code>,
<code class="function">sd_bus_open_system_remote()</code>, and
<code class="function">sd_bus_open_system_machine()</code> return a new
object and the caller owns the sole reference. When not needed
anymore, this reference should be destroyed with
<a href="sd_bus_unref.html"><span class="citerefentry"><span class="refentrytitle">sd_bus_unref</span>(3)</span></a>.
</p><p>The functions <code class="function">sd_bus_default_user()</code> and
<code class="function">sd_bus_default_system()</code> do not create a new
reference.</p></div><div class="refsect1"><a name="idm214201000368"></a><h2 id="Errors">Errors<a class="headerlink" title="Permalink to this headline" href="#Errors">¶</a></h2><p>Returned errors may indicate the following problems:</p><div class="variablelist"><p>In addition, any further connection-related errors may be
by returned. See <a href="sd_bus_send.html"><span class="citerefentry"><span class="refentrytitle">sd_bus_send</span>(3)</span></a>.</p><dl class="variablelist"><dt id="-EINVAL"><span class="term"><code class="varname">-EINVAL</code></span><a class="headerlink" title="Permalink to this term" href="#-EINVAL">¶</a></dt><dd><p>Specified parameter is invalid
(<code class="constant">NULL</code> in case of output
parameters).</p></dd><dt id="-ENOMEM"><span class="term"><code class="varname">-ENOMEM</code></span><a class="headerlink" title="Permalink to this term" href="#-ENOMEM">¶</a></dt><dd><p>Memory allocation failed.</p></dd></dl></div></div><div class="refsect1"><a name="idm214200994176"></a><h2 id="Notes">Notes<a class="headerlink" title="Permalink to this headline" href="#Notes">¶</a></h2><p><code class="function">sd_bus_open_user()</code> and other functions
described here are available as a shared library, which can be
compiled and linked to with the
<code class="constant">libsystemd</code> <a href="pkg-config.html"><span class="citerefentry"><span class="refentrytitle">pkg-config</span>(1)</span></a>
file.</p></div><div class="refsect1"><a name="idm214200991008"></a><h2 id="See Also">See Also<a class="headerlink" title="Permalink to this headline" href="#See%20Also">¶</a></h2><p>
<a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>,
<a href="sd-bus.html"><span class="citerefentry"><span class="refentrytitle">sd-bus</span>(3)</span></a>,
<a href="sd_bus_new.html"><span class="citerefentry"><span class="refentrytitle">sd_bus_new</span>(3)</span></a>,
<a href="sd_bus_ref.html"><span class="citerefentry"><span class="refentrytitle">sd_bus_ref</span>(3)</span></a>,
<a href="sd_bus_unref.html"><span class="citerefentry"><span class="refentrytitle">sd_bus_unref</span>(3)</span></a>,
<a href="ssh.html"><span class="citerefentry"><span class="refentrytitle">ssh</span>(1)</span></a>,
<a href="systemd-machined.service.html"><span class="citerefentry"><span class="refentrytitle">systemd-machined.service</span>(8)</span></a>,
<a href="machinectl.html"><span class="citerefentry"><span class="refentrytitle">machinectl</span>(1)</span></a>
</p></div></div></body></html>
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