systemctl: fix assertion hit by incorrect comparison

[thirdparty/systemd.git] / man / sd_session_is_active.xml

<?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">

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<refentry id="sd_session_is_active">

        <refentryinfo>
                <title>sd_session_is_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_session_is_active</refentrytitle>
                <manvolnum>3</manvolnum>
        </refmeta>

        <refnamediv>
                <refname>sd_session_is_active</refname>
                <refname>sd_session_get_state</refname>
                <refname>sd_session_get_uid</refname>
                <refname>sd_session_get_seat</refname>
                <refname>sd_session_get_service</refname>
                <refname>sd_session_get_type</refname>
                <refname>sd_session_get_class</refname>
                <refname>sd_session_get_display</refname>
                <refname>sd_session_get_tty</refname>
                <refpurpose>Determine state of a specific session</refpurpose>
        </refnamediv>

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

                        <funcprototype>
                                <funcdef>int <function>sd_session_is_active</function></funcdef>
                                <paramdef>const char* <parameter>session</parameter></paramdef>
                        </funcprototype>

                        <funcprototype>
                                <funcdef>int <function>sd_session_get_state</function></funcdef>
                                <paramdef>const char* <parameter>session</parameter></paramdef>
                                <paramdef>char** <parameter>state</parameter></paramdef>
                        </funcprototype>

                        <funcprototype>
                                <funcdef>int <function>sd_session_get_uid</function></funcdef>
                                <paramdef>const char* <parameter>session</parameter></paramdef>
                                <paramdef>uid_t* <parameter>uid</parameter></paramdef>
                        </funcprototype>

                        <funcprototype>
                                <funcdef>int <function>sd_session_get_seat</function></funcdef>
                                <paramdef>const char* <parameter>session</parameter></paramdef>
                                <paramdef>char** <parameter>seat</parameter></paramdef>
                        </funcprototype>

                        <funcprototype>
                                <funcdef>int <function>sd_session_get_service</function></funcdef>
                                <paramdef>const char* <parameter>session</parameter></paramdef>
                                <paramdef>char** <parameter>service</parameter></paramdef>
                        </funcprototype>

                        <funcprototype>
                                <funcdef>int <function>sd_session_get_type</function></funcdef>
                                <paramdef>const char* <parameter>session</parameter></paramdef>
                                <paramdef>char** <parameter>type</parameter></paramdef>
                        </funcprototype>

                        <funcprototype>
                                <funcdef>int <function>sd_session_get_class</function></funcdef>
                                <paramdef>const char* <parameter>session</parameter></paramdef>
                                <paramdef>char** <parameter>class</parameter></paramdef>
                        </funcprototype>

                        <funcprototype>
                                <funcdef>int <function>sd_session_get_display</function></funcdef>
                                <paramdef>const char* <parameter>session</parameter></paramdef>
                                <paramdef>char** <parameter>display</parameter></paramdef>
                        </funcprototype>

                        <funcprototype>
                                <funcdef>int <function>sd_session_get_tty</function></funcdef>
                                <paramdef>const char* <parameter>session</parameter></paramdef>
                                <paramdef>char** <parameter>tty</parameter></paramdef>
                        </funcprototype>
                </funcsynopsis>
        </refsynopsisdiv>

        <refsect1>
                <title>Description</title>

                <para><function>sd_session_is_active()</function> may
                be used to determine whether the session identified by
                the specified session identifier is currently active
                (i.e. currently in the foreground and available for
                user input) or not.</para>

                <para><function>sd_session_get_state()</function> may
                be used to determine the state of the session
                identified by the specified session identifier. The
                following states are currently known:
                <literal>online</literal> (session logged in, but
                session not active, i.e. not in the foreground),
                <literal>active</literal> (session logged in and
                active, i.e. in the foreground),
                <literal>closing</literal> (session nominally logged
                out, but some processes belonging to it 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. This function is a more generic version of
                <function>sd_session_is_active()</function>. 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_session_get_uid()</function> may be
                used to determine the user identifier of the Unix user the session
                identified by the specified session identifier belongs
                to.</para>

                <para><function>sd_session_get_seat()</function> may
                be used to determine the seat identifier of the seat
                the session identified by the specified session
                identifier belongs to. Note that not all sessions are
                attached to a seat, this call will fail for them. 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_session_get_service()</function>
                may be used to determine the name of the service (as
                passed during PAM session setup) that registered the
                session identified by the specified session
                identifier. 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_session_get_type()</function> may
                be used to determine the type of the session
                identified by the specified session identifier. The
                returned string is one of <literal>x11</literal>,
                <literal>tty</literal> or
                <literal>unspecified</literal> and needs to be freed
                with the libc
                <citerefentry><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
                call after use.</para>

                <para><function>sd_session_get_class()</function> may
                be used to determine the class of the session
                identified by the specified session identifier. The
                returned string is one of <literal>user</literal>,
                <literal>greeter</literal> or
                <literal>lock-screen</literal> and needs to be freed
                with the libc
                <citerefentry><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
                call after use.</para>

                <para><function>sd_session_get_display()</function>
                may be used to determine the X11 display of the
                session identified by the specified session
                identifier. The returned string is one of needs to be
                freed with the libc
                <citerefentry><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
                call after use.</para>

                <para><function>sd_session_get_tty()</function>
                may be used to determine the TTY device of the
                session identified by the specified session
                identifier. The returned string is one of needs to be
                freed with the libc
                <citerefentry><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
                call after use.</para>

                <para>If the <literal>session</literal> parameter of
                any of these functions is passed as NULL the operation
                is executed for the session the calling process is a
                member of, if there is any.</para>
        </refsect1>

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

                <para>If the test succeeds
                <function>sd_session_is_active()</function> returns a
                positive integer, if it fails 0.  On success
                <function>sd_session_get_state()</function>,
                <function>sd_session_get_uid()</function>,
                <function>sd_session_get_seat()</function>,
                <function>sd_session_get_service()</function>,
                <function>sd_session_get_type()</function>,
                <function>sd_session_get_class()</function>,
                <function>sd_session_get_display()</function> and
                <function>sd_session_get_tty()</function> return 0 or
                a positive integer. On failure, these calls return a
                negative errno-style error code.</para>
        </refsect1>

        <refsect1>
                <title>Notes</title>

                <para>The <function>sd_session_is_active()</function>,
                <function>sd_session_get_state()</function>,
                <function>sd_session_get_uid()</function>,
                <function>sd_session_get_seat()</function>,
                <function>sd_session_get_service()</function>,
                <function>sd_session_get_type()</function>,
                <function>sd_session_get_class()</function>,
                <function>sd_session_get_display()</function> and
                <function>sd_session_get_tty()</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>3</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>sd_pid_get_session</refentrytitle><manvolnum>3</manvolnum></citerefentry>
                </para>
        </refsect1>

</refentry>