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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><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><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><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>