sd_seat_get_active.xml 8.49 KB
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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
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  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
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  (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
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  Lesser General Public License for more details.
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  You should have received a copy of the GNU Lesser General Public License
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  along with systemd; If not, see <http://www.gnu.org/licenses/>.
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<refentry id="sd_seat_get_active" conditional='HAVE_PAM'>
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        <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 &lt;systemd/sd-login.h&gt;</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>
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                                <paramdef>const char* <parameter>seat</parameter></paramdef>
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                        </funcprototype>
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                        <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>
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                </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
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                user identifier parameter can be passed NULL, in
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                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
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                sessions in parallel (with only one being active at a
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                time).</para>
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                <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>

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                <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>
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        </refsect1>

        <refsect1>
                <title>Return Value</title>

                <para> On success
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                <function>sd_seat_get_active()</function>
                returns 0 or a positive integer. On success
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                <function>sd_seat_get_sessions()</function> returns
                the number of entries in the session identifier
                array. If the test succeeds
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                <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
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                calls return a negative errno-style error code.</para>
        </refsect1>

        <refsect1>
                <title>Notes</title>

                <para>The <function>sd_seat_get_active()</function>,
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                <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
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                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>,
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                        <citerefentry><refentrytitle>sd-login</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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                        <citerefentry><refentrytitle>sd_session_get_seat</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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                </para>
        </refsect1>

</refentry>