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<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>sd-login</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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</style><a href="index.html">Index </a>·
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<a href="../python-systemd/index.html">Python </a>·
<a href="../libudev/index.html">libudev </a>·
<a href="../libudev/index.html">gudev </a><span style="float:right">systemd 215</span><hr><div class="refentry"><a name="sd-login"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>sd-login — APIs for
tracking logins</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="funcsynopsis"><pre class="funcsynopsisinfo">#include <systemd/sd-login.h></pre></div><div class="cmdsynopsis"><p><code class="command">pkg-config --cflags --libs libsystemd</code> </p></div></div><div class="refsect1"><a name="idm214203511616"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description">¶</a></h2><p><code class="filename">sd-login.h</code> provides APIs to
introspect and monitor seat, login session and user
status information on the local system. </p><p>See <a class="ulink" href="http://www.freedesktop.org/wiki/Software/systemd/multiseat" target="_top">Multi-Seat
on Linux</a> for an introduction into multi-seat
support on Linux, the background for this set of APIs.</p><p>Note that these APIs only allow purely passive access
and monitoring of seats, sessions and users. To
actively make changes to the seat configuration,
terminate login sessions, or switch session on a seat
you need to utilize the D-Bus API of
systemd-logind, instead.</p><p>These functions synchronously access data in
<code class="filename">/proc</code>,
<code class="filename">/sys/fs/cgroup</code> and
<code class="filename">/run</code>. All of these are virtual
file systems, hence the runtime cost of the accesses
is relatively cheap.</p><p>It is possible (and often a very good choice) to
mix calls to the synchronous interface of
<code class="filename">sd-login.h</code> with the asynchronous
D-Bus interface of systemd-logind. However, if this is
done you need to think a bit about possible races
since the stream of events from D-Bus and from
<code class="filename">sd-login.h</code> interfaces such as the
login monitor are asynchronous and not ordered against
each other.</p><p>If the functions return string arrays, these are
generally <code class="constant">NULL</code> terminated and need to be freed by the
caller with the libc
<a href="free.html"><span class="citerefentry"><span class="refentrytitle">free</span>(3)</span></a>
call after use, including the strings referenced
therein. Similarly, individual strings returned need to
be freed, as well.</p><p>As a special exception, instead of an empty
string array <code class="constant">NULL</code> may be returned, which should be
treated equivalent to an empty string array.</p><p>See
<a href="sd_pid_get_session.html"><span class="citerefentry"><span class="refentrytitle">sd_pid_get_session</span>(3)</span></a>,
<a href="sd_uid_get_state.html"><span class="citerefentry"><span class="refentrytitle">sd_uid_get_state</span>(3)</span></a>,
<a href="sd_session_is_active.html"><span class="citerefentry"><span class="refentrytitle">sd_session_is_active</span>(3)</span></a>,
<a href="sd_seat_get_active.html"><span class="citerefentry"><span class="refentrytitle">sd_seat_get_active</span>(3)</span></a>,
<a href="sd_get_seats.html"><span class="citerefentry"><span class="refentrytitle">sd_get_seats</span>(3)</span></a>,
<a href="sd_login_monitor_new.html"><span class="citerefentry"><span class="refentrytitle">sd_login_monitor_new</span>(3)</span></a>
for more information about the functions
implemented.</p></div><div class="refsect1"><a name="idm214195679696"></a><h2 id="Notes">Notes<a class="headerlink" title="Permalink to this headline" href="#Notes">¶</a></h2><p><a name="pkgconfig-text"></a>These APIs are implemented 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="idm214199735312"></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_pid_get_session.html"><span class="citerefentry"><span class="refentrytitle">sd_pid_get_session</span>(3)</span></a>,
<a href="sd_uid_get_state.html"><span class="citerefentry"><span class="refentrytitle">sd_uid_get_state</span>(3)</span></a>,
<a href="sd_session_is_active.html"><span class="citerefentry"><span class="refentrytitle">sd_session_is_active</span>(3)</span></a>,
<a href="sd_seat_get_active.html"><span class="citerefentry"><span class="refentrytitle">sd_seat_get_active</span>(3)</span></a>,
<a href="sd_get_seats.html"><span class="citerefentry"><span class="refentrytitle">sd_get_seats</span>(3)</span></a>,
<a href="sd_login_monitor_new.html"><span class="citerefentry"><span class="refentrytitle">sd_login_monitor_new</span>(3)</span></a>,
<a href="sd-daemon.html"><span class="citerefentry"><span class="refentrytitle">sd-daemon</span>(3)</span></a>,
<a href="sd-readahead.html"><span class="citerefentry"><span class="refentrytitle">sd-readahead</span>(3)</span></a>,
<a href="pkg-config.html"><span class="citerefentry"><span class="refentrytitle">pkg-config</span>(1)</span></a>
</p></div></div></body></html>
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