systemd/man/sd_seat_get_active.xml

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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
        "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">

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<refentry id="sd_seat_get_active" conditional='HAVE_PAM'>

        <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>
                <refname>sd_seat_can_tty</refname>
                <refname>sd_seat_can_graphical</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 int *<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
                <constant>NULL</constant>, in case only one of the
                parameters shall be queried. The returned string needs
                to be freed with the libc
                <citerefentry project='man-pages'><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 (<constant>NULL</constant> 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
                <constant>NULL</constant> 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 project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
                call after use. Note that instead of an empty array
                <constant>NULL</constant> 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 <varname>seat</varname> parameter of any
                of these functions is passed as
                <constant>NULL</constant>, 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 a shared library, which can be compiled
                and linked to with the
                <constant>libsystemd</constant> <citerefentry project='die-net'><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>