1 <?xml version='
1.0'
?> <!--*-nxml-*-->
2 <!DOCTYPE refentry PUBLIC
"-//OASIS//DTD DocBook XML V4.5//EN"
3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
4 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
6 <refentry id=
"sd_seat_get_active" conditional='HAVE_PAM'
7 xmlns:
xi=
"http://www.w3.org/2001/XInclude">
10 <title>sd_seat_get_active
</title>
11 <productname>systemd
</productname>
15 <refentrytitle>sd_seat_get_active
</refentrytitle>
16 <manvolnum>3</manvolnum>
20 <refname>sd_seat_get_active
</refname>
21 <refname>sd_seat_get_sessions
</refname>
22 <refname>sd_seat_can_multi_session
</refname>
23 <refname>sd_seat_can_tty
</refname>
24 <refname>sd_seat_can_graphical
</refname>
25 <refpurpose>Determine state of a specific seat
</refpurpose>
30 <funcsynopsisinfo>#include
<systemd/sd-login.h
></funcsynopsisinfo>
33 <funcdef>int
<function>sd_seat_get_active
</function></funcdef>
34 <paramdef>const char *
<parameter>seat
</parameter></paramdef>
35 <paramdef>char **
<parameter>session
</parameter></paramdef>
36 <paramdef>uid_t *
<parameter>uid
</parameter></paramdef>
40 <funcdef>int
<function>sd_seat_get_sessions
</function></funcdef>
41 <paramdef>const char *
<parameter>seat
</parameter></paramdef>
42 <paramdef>char ***
<parameter>sessions
</parameter></paramdef>
43 <paramdef>uid_t **
<parameter>uid
</parameter></paramdef>
44 <paramdef>unsigned int *
<parameter>n_uids
</parameter></paramdef>
48 <funcdef>int
<function>sd_seat_can_multi_session
</function></funcdef>
49 <paramdef>const char *
<parameter>seat
</parameter></paramdef>
53 <funcdef>int
<function>sd_seat_can_tty
</function></funcdef>
54 <paramdef>const char *
<parameter>seat
</parameter></paramdef>
58 <funcdef>int
<function>sd_seat_can_graphical
</function></funcdef>
59 <paramdef>const char *
<parameter>seat
</parameter></paramdef>
65 <title>Description
</title>
67 <para><function>sd_seat_get_active()
</function> may be used to
68 determine which session is currently active on a seat, if there is
69 any. Returns the session identifier and the user identifier of the
70 Unix user the session is belonging to. Either the session or the
71 user identifier parameter can be passed
<constant>NULL
</constant>,
72 in case only one of the parameters shall be queried. The returned
73 string needs to be freed with the libc
74 <citerefentry project='man-pages'
><refentrytitle>free
</refentrytitle><manvolnum>3</manvolnum></citerefentry>
75 call after use.
</para>
77 <para><function>sd_seat_get_sessions()
</function> may be used to
78 determine all sessions on the specified seat. Returns two arrays,
79 one (
<constant>NULL
</constant> terminated) with the session
80 identifiers of the sessions and one with the user identifiers of
81 the Unix users the sessions belong to. An additional parameter may
82 be used to return the number of entries in the latter array. This
83 value is the same the return value, if the latter is nonnegative.
84 The two arrays and the last parameter may be passed as
85 <constant>NULL
</constant> in case these values need not to be
86 determined. The arrays and the strings referenced by them need to
87 be freed with the libc
88 <citerefentry project='man-pages'
><refentrytitle>free
</refentrytitle><manvolnum>3</manvolnum></citerefentry>
89 call after use. Note that instead of an empty array
90 <constant>NULL
</constant> may be returned and should be considered
91 equivalent to an empty array.
</para>
93 <para><function>sd_seat_can_multi_session()
</function> may be used
94 to determine whether a specific seat is capable of multi-session,
95 i.e. allows multiple login sessions in parallel (with only one
96 being active at a time).
</para>
98 <para><function>sd_seat_can_tty()
</function> may be used to
99 determine whether a specific seat provides TTY functionality, i.e.
100 is useful as a text console.
</para>
102 <para><function>sd_seat_can_graphical()
</function> may be used to
103 determine whether a specific seat provides graphics functionality,
104 i.e. is useful as a graphics display.
</para>
106 <para>If the
<varname>seat
</varname> parameter of any of these
107 functions is passed as
<constant>NULL
</constant>, the operation is
108 executed for the seat of the session of the calling process, if
113 <title>Return Value
</title>
115 <para> On success,
<function>sd_seat_get_active()
</function> returns
0 or a positive integer. On success,
116 <function>sd_seat_get_sessions()
</function> returns the number of entries in the session identifier
117 array. If the test succeeds,
<function>sd_seat_can_multi_session
</function>,
118 <function>sd_seat_can_tty
</function> and
<function>sd_seat_can_graphical
</function> return a positive
119 integer, if it fails
0. On failure, these calls return a negative errno-style error code.
</para>
122 <title>Errors
</title>
124 <para>Returned errors may indicate the following problems:
</para>
129 <term><constant>-ENODATA
</constant></term>
131 <listitem><para>The given field is not specified for the described seat.
</para>
136 <term><constant>-ENXIO
</constant></term>
138 <listitem><para>The specified seat is unknown.
</para>
143 <term><constant>-EINVAL
</constant></term>
145 <listitem><para>An input parameter was invalid (out of range, or
<constant>NULL
</constant>, where
146 that is not accepted).
</para></listitem>
150 <term><constant>-ENOMEM
</constant></term>
152 <listitem><para>Memory allocation failed.
</para></listitem>
158 <xi:include href=
"libsystemd-pkgconfig.xml" />
161 <title>See Also
</title>
164 <citerefentry><refentrytitle>systemd
</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
165 <citerefentry><refentrytitle>sd-login
</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
166 <citerefentry><refentrytitle>sd_session_get_seat
</refentrytitle><manvolnum>3</manvolnum></citerefentry>