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machined: optionally, allow registration of pre-existing units (scopes
[elogind.git] / man / sd_get_seats.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_get_seats" conditional='HAVE_PAM'>
25
26         <refentryinfo>
27                 <title>sd_get_seats</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_get_seats</refentrytitle>
42                 <manvolnum>3</manvolnum>
43         </refmeta>
44
45         <refnamediv>
46                 <refname>sd_get_seats</refname>
47                 <refname>sd_get_sessions</refname>
48                 <refname>sd_get_uids</refname>
49                 <refname>sd_get_machine_names</refname>
50                 <refpurpose>Determine available seats, sessions, logged in users and virtual machines/containers</refpurpose>
51         </refnamediv>
52
53         <refsynopsisdiv>
54                 <funcsynopsis>
55                         <funcsynopsisinfo>#include &lt;systemd/sd-login.h&gt;</funcsynopsisinfo>
56
57                         <funcprototype>
58                                 <funcdef>int <function>sd_get_seats</function></funcdef>
59                                 <paramdef>char*** <parameter>seats</parameter></paramdef>
60                         </funcprototype>
61
62                         <funcprototype>
63                                 <funcdef>int <function>sd_get_sessions</function></funcdef>
64                                 <paramdef>char*** <parameter>sessions</parameter></paramdef>
65                         </funcprototype>
66
67                         <funcprototype>
68                                 <funcdef>int <function>sd_get_uids</function></funcdef>
69                                 <paramdef>uid_t** <parameter>users</parameter></paramdef>
70                         </funcprototype>
71
72                         <funcprototype>
73                                 <funcdef>int <function>sd_get_machine_names</function></funcdef>
74                                 <paramdef>char*** <parameter>machines</parameter></paramdef>
75                         </funcprototype>
76
77                 </funcsynopsis>
78         </refsynopsisdiv>
79
80         <refsect1>
81                 <title>Description</title>
82
83                 <para><function>sd_get_seats()</function> may be used
84                 to determine all currently available local
85                 seats. Returns a <constant>NULL</constant> terminated array of seat
86                 identifiers. The returned array and all strings it
87                 references need to be freed with the libc
88                 <citerefentry><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>
92
93                 <para>Similarly, <function>sd_get_sessions()</function> may
94                 be used to determine all current login sessions.</para>
95
96                 <para>Similarly, <function>sd_get_uids()</function> may
97                 be used to determine all Unix users who currently have login sessions.</para>
98
99                 <para>Similarly,
100                 <function>sd_get_machine_names()</function> may be
101                 used to determine all current virtual machines and
102                 containers on the system.</para>
103
104                 <para>Note that the returned lists are not sorted and in an undefined order.</para>
105         </refsect1>
106
107         <refsect1>
108                 <title>Return Value</title>
109
110                 <para>On success, <function>sd_get_seats()</function>,
111                 <function>sd_get_sessions()</function>,
112                 <function>sd_get_uids()</function> and
113                 <function>sd_get_machine_names()</function> return the
114                 number of entries in the arrays. On failure, these
115                 calls return a negative errno-style error code.</para>
116         </refsect1>
117
118         <refsect1>
119                 <title>Notes</title>
120
121                 <para>The <function>sd_get_seats()</function>,
122                 <function>sd_get_sessions()</function>,
123                 <function>sd_get_uids()</function> and
124                 <function>sd_get_machine_names()</function> interfaces
125                 are available as a shared library, which can be compiled
126                 and linked to with the
127                 <constant>libsystemd-login</constant> <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
128                 file.</para>
129         </refsect1>
130
131         <refsect1>
132                 <title>See Also</title>
133
134                 <para>
135                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
136                         <citerefentry><refentrytitle>sd-login</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
137                         <citerefentry><refentrytitle>sd_session_get_seat</refentrytitle><manvolnum>3</manvolnum></citerefentry>
138                 </para>
139         </refsect1>
140
141 </refentry>