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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 project='man-pages'><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 project='man-pages'><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>Errors</title>

<para>Returned errors may indicate the following problems:</para>

<variablelist>

<varlistentry>

<term><constant>-ENODATA</constant></term>

<listitem><para>Given field is not specified for the described

seat.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><constant>-ENXIO</constant></term>

<listitem><para>The specified seat is unknown.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><constant>-EINVAL</constant></term>

<listitem><para>An input parameter was invalid (out of range,

or NULL, where that's not accepted).</para></listitem>

</varlistentry>

<varlistentry>

<term><constant>-ENOMEM</constant></term>

<listitem><para>Memory allocation failed.</para></listitem>

</varlistentry>

</variablelist>

</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 project='die-net'><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>