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NEWS: mention set-log-level, --user, --system
[elogind.git] / man / sd-login.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-login" conditional='HAVE_PAM'>
25
26         <refentryinfo>
27                 <title>sd-login</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-login</refentrytitle>
42                 <manvolnum>3</manvolnum>
43         </refmeta>
44
45         <refnamediv>
46                 <refname>sd-login</refname>
47                 <refpurpose>APIs for
48                 tracking logins</refpurpose>
49         </refnamediv>
50
51         <refsynopsisdiv>
52                 <funcsynopsis>
53                         <funcsynopsisinfo>#include &lt;systemd/sd-login.h&gt;</funcsynopsisinfo>
54                 </funcsynopsis>
55
56                 <cmdsynopsis>
57                         <command>pkg-config --cflags --libs libsystemd-login</command>
58                 </cmdsynopsis>
59         </refsynopsisdiv>
60
61         <refsect1>
62                 <title>Description</title>
63
64                 <para><filename>sd-login.h</filename> provides APIs to
65                 introspect and monitor seat, login session and user
66                 status information on the local system. </para>
67
68                 <para>See <ulink
69                 url="http://www.freedesktop.org/wiki/Software/systemd/multiseat">Multi-Seat
70                 on Linux</ulink> for an introduction into multi-seat
71                 support on Linux, the background for this set of APIs.</para>
72
73                 <para>Note that these APIs only allow purely passive access
74                 and monitoring of seats, sessions and users. To
75                 actively make changes to the seat configuration,
76                 terminate login sessions, or switch session on a seat
77                 you need to utilize the D-Bus API of
78                 systemd-logind, instead.</para>
79
80                 <para>These functions synchronously access data in
81                 <filename>/proc</filename>,
82                 <filename>/sys/fs/cgroup</filename> and
83                 <filename>/run</filename>. All of these are virtual
84                 file systems, hence the runtime cost of the accesses
85                 is relatively cheap.</para>
86
87                 <para>It is possible (and often a very good choice) to
88                 mix calls to the synchronous interface of
89                 <filename>sd-login.h</filename> with the asynchronous
90                 D-Bus interface of systemd-logind. However, if this is
91                 done you need to think a bit about possible races
92                 since the stream of events from D-Bus and from
93                 <filename>sd-login.h</filename> interfaces such as the
94                 login monitor are asynchronous and not ordered against
95                 each other.</para>
96
97                 <para>If the functions return string arrays, these are
98                 generally <constant>NULL</constant> terminated and need to be freed by the
99                 caller with the libc
100                 <citerefentry><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
101                 call after use, including the strings referenced
102                 therein. Similar, individual strings returned need to
103                 be freed, as well.</para>
104
105                 <para>As a special exception, instead of an empty
106                 string array <constant>NULL</constant> may be returned, which should be
107                 treated equivalent to an empty string array.</para>
108
109                 <para>See
110                 <citerefentry><refentrytitle>sd_pid_get_session</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
111                 <citerefentry><refentrytitle>sd_uid_get_state</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
112                 <citerefentry><refentrytitle>sd_session_is_active</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
113                 <citerefentry><refentrytitle>sd_seat_get_active</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
114                 <citerefentry><refentrytitle>sd_get_seats</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
115                 <citerefentry><refentrytitle>sd_login_monitor_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>
116                 for more information about the functions
117                 implemented.</para>
118         </refsect1>
119
120         <refsect1>
121                 <title>Notes</title>
122
123                 <para>These APIs are implemented as shared library,
124                 which can be compiled and linked to with the
125                 <constant>libsystemd-login</constant> <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
126                 file.</para>
127         </refsect1>
128
129         <refsect1>
130                 <title>See Also</title>
131                 <para>
132                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
133                         <citerefentry><refentrytitle>sd_pid_get_session</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
134                         <citerefentry><refentrytitle>sd_uid_get_state</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
135                         <citerefentry><refentrytitle>sd_session_is_active</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
136                         <citerefentry><refentrytitle>sd_seat_get_active</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
137                         <citerefentry><refentrytitle>sd_get_seats</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
138                         <citerefentry><refentrytitle>sd_login_monitor_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
139                         <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
140                         <citerefentry><refentrytitle>sd-readahead</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
141                         <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
142                 </para>
143         </refsect1>
144
145 </refentry>