systemd/man/sd_get_seats.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_get_seats" conditional='HAVE_PAM'>

        <refentryinfo>
                <title>sd_get_seats</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_get_seats</refentrytitle>
                <manvolnum>3</manvolnum>
        </refmeta>

        <refnamediv>
                <refname>sd_get_seats</refname>
                <refname>sd_get_sessions</refname>
                <refname>sd_get_uids</refname>
                <refname>sd_get_machine_names</refname>
                <refpurpose>Determine available seats, sessions, logged in users and virtual machines/containers</refpurpose>
        </refnamediv>

        <refsynopsisdiv>
                <funcsynopsis>
                        <funcsynopsisinfo>#include &lt;systemd/sd-login.h&gt;</funcsynopsisinfo>

                        <funcprototype>
                                <funcdef>int <function>sd_get_seats</function></funcdef>
                                <paramdef>char*** <parameter>seats</parameter></paramdef>
                        </funcprototype>

                        <funcprototype>
                                <funcdef>int <function>sd_get_sessions</function></funcdef>
                                <paramdef>char*** <parameter>sessions</parameter></paramdef>
                        </funcprototype>

                        <funcprototype>
                                <funcdef>int <function>sd_get_uids</function></funcdef>
                                <paramdef>uid_t** <parameter>users</parameter></paramdef>
                        </funcprototype>

                        <funcprototype>
                                <funcdef>int <function>sd_get_machine_names</function></funcdef>
                                <paramdef>char*** <parameter>machines</parameter></paramdef>
                        </funcprototype>

                </funcsynopsis>
        </refsynopsisdiv>

        <refsect1>
                <title>Description</title>

                <para><function>sd_get_seats()</function> may be used
                to determine all currently available local
                seats. Returns a <constant>NULL</constant> terminated array of seat
                identifiers. The returned array and all strings it
                references 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
                <constant>NULL</constant> may be returned and should be considered
                equivalent to an empty array.</para>

                <para>Similarly, <function>sd_get_sessions()</function> may
                be used to determine all current login sessions.</para>

                <para>Similarly, <function>sd_get_uids()</function> may
                be used to determine all Unix users who currently have login sessions.</para>

                <para>Similarly,
                <function>sd_get_machine_names()</function> may be
                used to determine all current virtual machines and
                containers on the system.</para>

                <para>Note that the returned lists are not sorted and in an undefined order.</para>
        </refsect1>

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

                <para>On success, <function>sd_get_seats()</function>,
                <function>sd_get_sessions()</function>,
                <function>sd_get_uids()</function> and
                <function>sd_get_machine_names()</function> return the
                number of entries in the arrays. On failure, these
                calls return a negative errno-style error code.</para>
        </refsect1>

        <refsect1>
                <title>Notes</title>

                <para>The <function>sd_get_seats()</function>,
                <function>sd_get_sessions()</function>,
                <function>sd_get_uids()</function> and
                <function>sd_get_machine_names()</function> interfaces
                are available as a shared library, which can be compiled
                and linked to with the
                <constant>libsystemd</constant> <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>