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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<refentry id= "sd_seat_get_active" >
<refentryinfo >
<title > sd_seat_get_active</title>
<productname > systemd</productname>
<authorgroup >
<author >
<contrib > Developer</contrib>
<firstname > Lennart</firstname>
<surname > Poettering</surname>
<email > lennart@poettering.net</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta >
<refentrytitle > sd_seat_get_active</refentrytitle>
<manvolnum > 3</manvolnum>
</refmeta>
<refnamediv >
<refname > sd_seat_get_active</refname>
<refname > sd_seat_get_sessions</refname>
<refname > sd_seat_can_multi_session</refname>
<refpurpose > Determine state of a specific seat</refpurpose>
</refnamediv>
<refsynopsisdiv >
<funcsynopsis >
<funcsynopsisinfo > #include < systemd/sd-login.h> </funcsynopsisinfo>
<funcprototype >
<funcdef > int <function > sd_seat_get_active</function> </funcdef>
<paramdef > const char* <parameter > seat</parameter> </paramdef>
<paramdef > char** <parameter > session</parameter> </paramdef>
<paramdef > uid_t* <parameter > uid</parameter> </paramdef>
</funcprototype>
<funcprototype >
<funcdef > int <function > sd_seat_get_sessions</function> </funcdef>
<paramdef > const char* <parameter > seat</parameter> </paramdef>
<paramdef > char*** <parameter > sessions</parameter> </paramdef>
<paramdef > uid_t** <parameter > uid</parameter> </paramdef>
<paramdef > unsigned* <parameter > n_uids</parameter> </paramdef>
</funcprototype>
<funcprototype >
<funcdef > int <function > sd_seat_can_multi_session</function> </funcdef>
<paramdef > const char* <parameter > session</parameter> </paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1 >
<title > Description</title>
<para > <function > sd_seat_get_active()</function> may be
used to determine which session is currently active on
a seat, if there is any. Returns the session
identifier and the user identifier of the Unix user
the session is belonging to. Either the session or the
user identifier parameter can be be passed NULL, in
case only one of the parameters shall be queried. The
returned string needs to be freed with the libc
<citerefentry > <refentrytitle > free</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry>
call after use.</para>
<para > <function > sd_seat_get_sessions()</function> may
be used to determine all sessions on the specified
seat. Returns two arrays, one (NULL terminated) with
the session identifiers of the sessions and one with
the user identifiers of the Unix users the sessions
belong to. An additional parameter may be used to
return the number of entries in the latter array. The
two arrays and the latter parameter may be passed as
NULL in case these values need not to be
determined. The arrays and the strings referenced by
them need to be freed with the libc
<citerefentry > <refentrytitle > free</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry>
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call after use. Note that instead of an empty array
NULL may be returned and should be considered
equivalent to an empty array.</para>
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<para > <function > sd_seat_can_multi_session()</function>
may be used to determine whether a specific seat is
capable of multi-session, i.e. allows multiple login
sessions in parallel (whith only one being active at a
time).</para>
</refsect1>
<refsect1 >
<title > Return Value</title>
<para > On success
<function > sd_seat_get_active()</function> return
return 0 or a positive integer. On success
<function > sd_seat_get_sessions()</function> returns
the number of entries in the session identifier
array. If the test succeeds
<function > sd_seat_can_multi_session</function> returns
a positive integer, if it fails 0. On failure, these
calls return a negative errno-style error code.</para>
</refsect1>
<refsect1 >
<title > Notes</title>
<para > The <function > sd_seat_get_active()</function> ,
<function > sd_seat_get_sessions()</function> , and
<function > sd_seat_can_multi_session()</function> interfaces
are available as shared library, which can be compiled
and linked to with the
<literal > libsystemd-login</literal>
<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-login</refentrytitle> <manvolnum > 7</manvolnum> </citerefentry> ,
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<citerefentry > <refentrytitle > sd_session_get_seat</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry>
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</para>
</refsect1>
</refentry>
