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<a href="../libudev/index.html">gudev </a><span style="float:right">systemd 219</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="idm139759439635504"></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
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object and opens a connection to the user bus.
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<code class="function">sd_bus_open_system()</code> does the same, but
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connects to the system bus.</p><p>If the <code class="varname">$DBUS_SESSION_BUS_ADDRESS</code> environment
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variable is set
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(cf. <a href="http://man7.org/linux/man-pages/man7/environ.7.html"><span class="citerefentry"><span class="refentrytitle">environ</span>(7)</span></a>),
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it will be used as the address of the user bus. This variable can
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contain multiple addresses separated by "<code class="literal">;</code>". If
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this variable is not set, a suitable default for the default user
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D-Bus instance will be used.</p><p>If the <code class="varname">$DBUS_SYSTEM_BUS_ADDRESS</code> environment
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variable is set, it will be used as the address of the system
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bus. This variable uses the same syntax as
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<code class="varname">$DBUS_SESSION_BUS_ADDRESS</code>/. If this variable is
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not set, a suitable default for the default system D-Bus instance
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will be used.</p><p><code class="function">sd_bus_open_system_remote()</code> connects to
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the system bus on the specified <em class="parameter"><code>host</code></em> using
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SSH. <em class="parameter"><code>host</code></em> consists of an optional user name
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followed by the "<code class="literal">@</code>" symbol, and the hostname.
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</p><p><code class="function">sd_bus_open_system_container()</code> connects
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to the system bus in the specified <em class="parameter"><code>machine</code></em>,
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where <em class="parameter"><code>machine</code></em> is the name of a container.
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See
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<a href="machinectl.html"><span class="citerefentry"><span class="refentrytitle">machinectl</span>(1)</span></a>
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for more information about "machines".</p><p><code class="function">sd_bus_default_user()</code> returns a bus
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object connected to the user bus. Each thread has its own object, but it
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may be passed around. It is created on the first invocation of
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<code class="function">sd_bus_default_user()</code>, and subsequent
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invocations returns a reference to the same object.</p><p><code class="function">sd_bus_default_system()</code> is similar to
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<code class="function">sd_bus_default_user()</code>, but connects to the
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system bus.</p></div><div class="refsect1"><a name="idm139759443521376"></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
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integer. On failure, these calls return a negative
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errno-style error code.</p></div><div class="refsect1"><a name="idm139759443520048"></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>,
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<code class="function">sd_bus_open_system()</code>,
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<code class="function">sd_bus_open_system_remote()</code>, and
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<code class="function">sd_bus_open_system_machine()</code> return a new
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object and the caller owns the sole reference. When not needed
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anymore, this reference should be destroyed with
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<a href="sd_bus_unref.html"><span class="citerefentry"><span class="refentrytitle">sd_bus_unref</span>(3)</span></a>.
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</p><p>The functions <code class="function">sd_bus_default_user()</code> and
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<code class="function">sd_bus_default_system()</code> do not create a new
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reference.</p></div><div class="refsect1"><a name="idm139759443505904"></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
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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="constant">-EINVAL</code></span><a class="headerlink" title="Permalink to this term" href="#-EINVAL">¶</a></dt><dd><p>Specified parameter is invalid
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(<code class="constant">NULL</code> in case of output
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parameters).</p></dd><dt id="-ENOMEM"><span class="term"><code class="constant">-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="idm139759443499760"></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
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described here are available as a shared library, which can be
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compiled and linked to with the
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<code class="constant">libsystemd</code> <a href="http://linux.die.net/man/1/pkg-config"><span class="citerefentry"><span class="refentrytitle">pkg-config</span>(1)</span></a>
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file.</p></div><div class="refsect1"><a name="idm139759443496320"></a><h2 id="See Also">See Also<a class="headerlink" title="Permalink to this headline" href="#See%20Also">¶</a></h2><p>
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<a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>,
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<a href="sd-bus.html"><span class="citerefentry"><span class="refentrytitle">sd-bus</span>(3)</span></a>,
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<a href="sd_bus_new.html"><span class="citerefentry"><span class="refentrytitle">sd_bus_new</span>(3)</span></a>,
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<a href="sd_bus_ref.html"><span class="citerefentry"><span class="refentrytitle">sd_bus_ref</span>(3)</span></a>,
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<a href="sd_bus_unref.html"><span class="citerefentry"><span class="refentrytitle">sd_bus_unref</span>(3)</span></a>,
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<a href="ssh.html"><span class="citerefentry"><span class="refentrytitle">ssh</span>(1)</span></a>,
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<a href="systemd-machined.service.html"><span class="citerefentry"><span class="refentrytitle">systemd-machined.service</span>(8)</span></a>,
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<a href="machinectl.html"><span class="citerefentry"><span class="refentrytitle">machinectl</span>(1)</span></a>
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</p></div></div></body></html>
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