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[elogind.git] / man / sd_seat_get_active.xml
1 <?xml version='1.0'?> <!--*-nxml-*-->
2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
3         "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
4
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8   Copyright 2010 Lennart Poettering
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23
24 <refentry id="sd_seat_get_active" conditional='HAVE_PAM'>
25
26         <refentryinfo>
27                 <title>sd_seat_get_active</title>
28                 <productname>systemd</productname>
29
30                 <authorgroup>
31                         <author>
32                                 <contrib>Developer</contrib>
33                                 <firstname>Lennart</firstname>
34                                 <surname>Poettering</surname>
35                                 <email>lennart@poettering.net</email>
36                         </author>
37                 </authorgroup>
38         </refentryinfo>
39
40         <refmeta>
41                 <refentrytitle>sd_seat_get_active</refentrytitle>
42                 <manvolnum>3</manvolnum>
43         </refmeta>
44
45         <refnamediv>
46                 <refname>sd_seat_get_active</refname>
47                 <refname>sd_seat_get_sessions</refname>
48                 <refname>sd_seat_can_multi_session</refname>
49                 <refname>sd_seat_can_tty</refname>
50                 <refname>sd_seat_can_graphical</refname>
51                 <refpurpose>Determine state of a specific seat</refpurpose>
52         </refnamediv>
53
54         <refsynopsisdiv>
55                 <funcsynopsis>
56                         <funcsynopsisinfo>#include &lt;systemd/sd-login.h&gt;</funcsynopsisinfo>
57
58                         <funcprototype>
59                                 <funcdef>int <function>sd_seat_get_active</function></funcdef>
60                                 <paramdef>const char *<parameter>seat</parameter></paramdef>
61                                 <paramdef>char **<parameter>session</parameter></paramdef>
62                                 <paramdef>uid_t *<parameter>uid</parameter></paramdef>
63                         </funcprototype>
64
65                         <funcprototype>
66                                 <funcdef>int <function>sd_seat_get_sessions</function></funcdef>
67                                 <paramdef>const char *<parameter>seat</parameter></paramdef>
68                                 <paramdef>char ***<parameter>sessions</parameter></paramdef>
69                                 <paramdef>uid_t **<parameter>uid</parameter></paramdef>
70                                 <paramdef>unsigned int *<parameter>n_uids</parameter></paramdef>
71                         </funcprototype>
72
73                         <funcprototype>
74                                 <funcdef>int <function>sd_seat_can_multi_session</function></funcdef>
75                                 <paramdef>const char *<parameter>seat</parameter></paramdef>
76                         </funcprototype>
77
78                         <funcprototype>
79                                 <funcdef>int <function>sd_seat_can_tty</function></funcdef>
80                                 <paramdef>const char *<parameter>seat</parameter></paramdef>
81                         </funcprototype>
82
83                         <funcprototype>
84                                 <funcdef>int <function>sd_seat_can_graphical</function></funcdef>
85                                 <paramdef>const char *<parameter>seat</parameter></paramdef>
86                         </funcprototype>
87                 </funcsynopsis>
88         </refsynopsisdiv>
89
90         <refsect1>
91                 <title>Description</title>
92
93                 <para><function>sd_seat_get_active()</function> may be
94                 used to determine which session is currently active on
95                 a seat, if there is any. Returns the session
96                 identifier and the user identifier of the Unix user
97                 the session is belonging to. Either the session or the
98                 user identifier parameter can be passed
99                 <constant>NULL</constant>, in case only one of the
100                 parameters shall be queried. The returned string needs
101                 to be freed with the libc
102                 <citerefentry><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
103                 call after use.</para>
104
105                 <para><function>sd_seat_get_sessions()</function> may
106                 be used to determine all sessions on the specified
107                 seat. Returns two arrays, one (<constant>NULL</constant> terminated) with
108                 the session identifiers of the sessions and one with
109                 the user identifiers of the Unix users the sessions
110                 belong to. An additional parameter may be used to
111                 return the number of entries in the latter array. The
112                 two arrays and the latter parameter may be passed as
113                 <constant>NULL</constant> in case these values need not to be
114                 determined. The arrays and the strings referenced by
115                 them need to be freed with the libc
116                 <citerefentry><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
117                 call after use. Note that instead of an empty array
118                 <constant>NULL</constant> may be returned and should be considered
119                 equivalent to an empty array.</para>
120
121                 <para><function>sd_seat_can_multi_session()</function>
122                 may be used to determine whether a specific seat is
123                 capable of multi-session, i.e. allows multiple login
124                 sessions in parallel (with only one being active at a
125                 time).</para>
126
127                 <para><function>sd_seat_can_tty()</function> may be
128                 used to determine whether a specific seat provides TTY
129                 functionality, i.e. is useful as a text console.</para>
130
131                 <para><function>sd_seat_can_graphical()</function> may
132                 be used to determine whether a specific seat provides
133                 graphics functionality, i.e. is useful as a graphics
134                 display.</para>
135
136                 <para>If the <varname>seat</varname> parameter of any
137                 of these functions is passed as
138                 <constant>NULL</constant>, the operation is executed
139                 for the seat of the session of the calling process, if
140                 there is any.</para>
141         </refsect1>
142
143         <refsect1>
144                 <title>Return Value</title>
145
146                 <para> On success,
147                 <function>sd_seat_get_active()</function>
148                 returns 0 or a positive integer. On success,
149                 <function>sd_seat_get_sessions()</function> returns
150                 the number of entries in the session identifier
151                 array. If the test succeeds,
152                 <function>sd_seat_can_multi_session</function>,
153                 <function>sd_seat_can_tty</function> and
154                 <function>sd_seat_can_graphical</function> return a
155                 positive integer, if it fails 0. On failure, these
156                 calls return a negative errno-style error code.</para>
157         </refsect1>
158
159         <refsect1>
160                 <title>Notes</title>
161
162                 <para>The <function>sd_seat_get_active()</function>,
163                 <function>sd_seat_get_sessions()</function>,
164                 <function>sd_seat_can_multi_session()</function>,
165                 <function>sd_seat_can_tty()</function> and
166                 <function>sd_seat_can_grapical()</function> interfaces
167                 are available as a shared library, which can be compiled
168                 and linked to with the
169                 <constant>libsystemd</constant> <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
170                 file.</para>
171         </refsect1>
172
173         <refsect1>
174                 <title>See Also</title>
175
176                 <para>
177                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
178                         <citerefentry><refentrytitle>sd-login</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
179                         <citerefentry><refentrytitle>sd_session_get_seat</refentrytitle><manvolnum>3</manvolnum></citerefentry>
180                 </para>
181         </refsect1>
182
183 </refentry>