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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   6   This file is part of systemd.
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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. Similarly, 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 a 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>