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<?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 2010 Lennart Poettering
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_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>seat</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_seat_can_tty</function></funcdef>
<paramdef>const char* <parameter>seat</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_seat_can_graphical</function></funcdef>
<paramdef>const char* <parameter>seat</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 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>
call after use. Note that instead of an empty array
NULL may be returned and should be considered
equivalent to an empty array.</para>
<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 (with only one being active at a
time).</para>
<para><function>sd_seat_can_tty()</function> may be
used to determine whether a specific seat provides TTY
functionality, i.e. is useful as a text console.</para>
<para><function>sd_seat_can_graphical()</function> may
be used to determine whether a specific seat provides
graphics functionality, i.e. is useful as a graphics
display.</para>
<para>If the <literal>seat</literal> parameter of any
of these functions is passed as NULL the operation is
executed for the seat of the session of the calling
process, if there is any.</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para> On success
<function>sd_seat_get_active()</function>
returns 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>,
<function>sd_seat_can_tty</function> and
<function>sd_seat_can_graphical</function> return 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>,
<function>sd_seat_can_multi_session()</function>,
<function>sd_seat_can_tty()</function> and
<function>sd_seat_can_grapical()</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>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_session_get_seat</refentrytitle><manvolnum>3</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
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