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">

        <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>
                <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>
                </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), <literal>active</literal> (user logged in on
                an active seat). 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. 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. Acceptes a Unix user identifier as
                parameter. The <parameter>require_active</parameter>
                boolean parameter controls whether the returned list
                shall consist of only those sessions where the user is
                currently active (true) or where the user is currently
                logged in at all, possibly inactive (false). The call
                returns a NULL 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
                NULL 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 NULL may
                be returned and should be considered equivalent to an
                empty array.</para>

                <para>Similar, <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>
        </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. On failure,
                these calls return a negative errno-style error
                code.</para>
        </refsect1>

        <refsect1>
                <title>Notes</title>

                <para>The <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> 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>7</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>sd_pid_get_owner_uid</refentrytitle><manvolnum>3</manvolnum></citerefentry>
                </para>
        </refsect1>

</refentry>