systemd/man/sd_uid_get_state.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_uid_get_state" conditional='HAVE_PAM'>

        <refentryinfo>
                <title>sd_uid_get_state</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_uid_get_state</refentrytitle>
                <manvolnum>3</manvolnum>
        </refmeta>

        <refnamediv>
                <refname>sd_uid_get_state</refname>
                <refname>sd_uid_is_on_seat</refname>
                <refname>sd_uid_get_sessions</refname>
                <refname>sd_uid_get_seats</refname>
                <refname>sd_uid_get_display</refname>
                <refpurpose>Determine login state of a specific Unix user ID</refpurpose>
        </refnamediv>

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

                        <funcprototype>
                                <funcdef>int <function>sd_uid_get_state</function></funcdef>
                                <paramdef>uid_t <parameter>uid</parameter></paramdef>
                                <paramdef>char **<parameter>state</parameter></paramdef>
                        </funcprototype>

                        <funcprototype>
                                <funcdef>int <function>sd_uid_is_on_seat</function></funcdef>
                                <paramdef>uid_t <parameter>uid</parameter></paramdef>
                                <paramdef>int <parameter>require_active</parameter></paramdef>
                                <paramdef>const char *<parameter>seat</parameter></paramdef>
                        </funcprototype>

                        <funcprototype>
                                <funcdef>int <function>sd_uid_get_sessions</function></funcdef>
                                <paramdef>uid_t <parameter>uid</parameter></paramdef>
                                <paramdef>int <parameter>require_active</parameter></paramdef>
                                <paramdef>char ***<parameter>sessions</parameter></paramdef>
                        </funcprototype>

                        <funcprototype>
                                <funcdef>int <function>sd_uid_get_seats</function></funcdef>
                                <paramdef>uid_t <parameter>uid</parameter></paramdef>
                                <paramdef>int <parameter>require_active</parameter></paramdef>
                                <paramdef>char ***<parameter>seats</parameter></paramdef>
                        </funcprototype>

                        <funcprototype>
                                <funcdef>int <function>sd_uid_get_display</function></funcdef>
                                <paramdef>uid_t <parameter>uid</parameter></paramdef>
                                <paramdef>char **<parameter>session</parameter></paramdef>
                        </funcprototype>
                </funcsynopsis>
        </refsynopsisdiv>

        <refsect1>
                <title>Description</title>

                <para><function>sd_uid_get_state()</function> may be
                used to determine the login state of a specific Unix
                user identifier. The following states are currently
                known: <literal>offline</literal> (user not logged in
                at all), <literal>lingering</literal> (user not logged
                in, but some user services running),
                <literal>online</literal> (user logged in, but not
                active, i.e. has no session in the foreground),
                <literal>active</literal> (user logged in, and has at
                least one active session, i.e. one session in the
                foreground), <literal>closing</literal> (user not
                logged in, and not lingering, but some processes are
                still around). In the future additional states might
                be defined, client code should be written to be robust
                in regards to additional state strings being
                returned. 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_uid_is_on_seat()</function> may be
                used to determine whether a specific user is logged in
                or active on a specific seat. Accepts a Unix user
                identifier and a seat identifier string as
                parameters. The <parameter>require_active</parameter>
                parameter is a boolean value. If non-zero (true), this
                function will test if the user is active (i.e. has a
                session that is in the foreground and accepting user
                input) on the specified seat, otherwise (false) only
                if the user is logged in (and possibly inactive) on
                the specified seat.</para>

                <para><function>sd_uid_get_sessions()</function> may
                be used to determine the current sessions of the
                specified user. Accepts a Unix user identifier as
                parameter. The <parameter>require_active</parameter>
                parameter controls whether the returned list shall
                consist of only those sessions where the user is
                currently active (&gt; 0), where the user is currently
                online but possibly inactive (= 0), or
                logged in at all but possibly closing the session (&lt; 0). The call returns a
                <constant>NULL</constant> terminated string array of session identifiers in
                <parameter>sessions</parameter> which needs to be
                freed by the caller with the libc
                <citerefentry><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
                call after use, including all the strings
                referenced. If the string array parameter is passed as
                <constant>NULL</constant>, the array will not be filled in, but the return
                code still indicates the number of current
                sessions. 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_uid_get_seats()</function>
                may be used to determine the list of seats on which
                the user currently has sessions. Similar semantics
                apply, however note that the user may have
                multiple sessions on the same seat as well as sessions
                with no attached seat and hence the number of entries
                in the returned array may differ from the one returned
                by <function>sd_uid_get_sessions()</function>.</para>

                <para><function>sd_uid_get_display()</function>
                returns the name of the "primary" session of a user.
                If the user has graphical sessions, it will be the
                oldest graphical session. Otherwise, it will be the
                oldest open session.</para>
        </refsect1>

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

                <para>On success,
                <function>sd_uid_get_state()</function> returns 0 or a
                positive integer. If the test succeeds,
                <function>sd_uid_is_on_seat()</function> returns a
                positive integer; if it fails,
                0. <function>sd_uid_get_sessions()</function> and
                <function>sd_uid_get_seats()</function> return the
                number of entries in the returned arrays.
                <function>sd_uid_get_display()</function> returns
                a non-negative code on success. On failure,
                these calls return a negative errno-style error
                code.</para>
        </refsect1>

        <refsect1>
                <title>Notes</title>

                <para>Functions described here are available as a
                shared library, and can be compiled and linked to
                using the
                <constant>libsystemd</constant> <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
                entry.</para>
        </refsect1>

        <refsect1>
                <title>History</title>

                <function>sd_uid_get_state()</function>,
                <function>sd_uid_is_on_seat()</function>,
                <function>sd_uid_get_sessions()</function>,
                and <function>sd_uid_get_seats()</function> functions
                were added in systemd-31.

                <para><function>sd_uid_get_display()</function> was
                added in systemd-213.</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_pid_get_owner_uid</refentrytitle><manvolnum>3</manvolnum></citerefentry>
                </para>
        </refsect1>

</refentry>