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
   5 <!--
   6   This file is part of systemd.
   7
   8   Copyright 2010 Lennart Poettering
   9
  10   systemd is free software; you can redistribute it and/or modify it
  11   under the terms of the GNU Lesser General Public License as published by
  12   the Free Software Foundation; either version 2.1 of the License, or
  13   (at your option) any later version.
  14
  15   systemd is distributed in the hope that it will be useful, but
  16   WITHOUT ANY WARRANTY; without even the implied warranty of
  17   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  18   Lesser General Public License for more details.
  19
  20   You should have received a copy of the GNU Lesser General Public License
  21   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  22 -->
  23
  24 <refentry id="sd-login" conditional='HAVE_PAM'
  25         xmlns:xi="http://www.w3.org/2001/XInclude">
  26
  27         <refentryinfo>
  28                 <title>sd-login</title>
  29                 <productname>systemd</productname>
  30
  31                 <authorgroup>
  32                         <author>
  33                                 <contrib>Developer</contrib>
  34                                 <firstname>Lennart</firstname>
  35                                 <surname>Poettering</surname>
  36                                 <email>lennart@poettering.net</email>
  37                         </author>
  38                 </authorgroup>
  39         </refentryinfo>
  40
  41         <refmeta>
  42                 <refentrytitle>sd-login</refentrytitle>
  43                 <manvolnum>3</manvolnum>
  44         </refmeta>
  45
  46         <refnamediv>
  47                 <refname>sd-login</refname>
  48                 <refpurpose>APIs for
  49                 tracking logins</refpurpose>
  50         </refnamediv>
  51
  52         <refsynopsisdiv>
  53                 <funcsynopsis>
  54                         <funcsynopsisinfo>#include &lt;systemd/sd-login.h&gt;</funcsynopsisinfo>
  55                 </funcsynopsis>
  56
  57                 <cmdsynopsis>
  58                         <command>pkg-config --cflags --libs libsystemd</command>
  59                 </cmdsynopsis>
  60         </refsynopsisdiv>
  61
  62         <refsect1>
  63                 <title>Description</title>
  64
  65                 <para><filename>sd-login.h</filename> provides APIs to
  66                 introspect and monitor seat, login session and user
  67                 status information on the local system. </para>
  68
  69                 <para>See <ulink
  70                 url="http://www.freedesktop.org/wiki/Software/systemd/multiseat">Multi-Seat
  71                 on Linux</ulink> for an introduction into multi-seat
  72                 support on Linux, the background for this set of APIs.</para>
  73
  74                 <para>Note that these APIs only allow purely passive access
  75                 and monitoring of seats, sessions and users. To
  76                 actively make changes to the seat configuration,
  77                 terminate login sessions, or switch session on a seat
  78                 you need to utilize the D-Bus API of
  79                 systemd-logind, instead.</para>
  80
  81                 <para>These functions synchronously access data in
  82                 <filename>/proc</filename>,
  83                 <filename>/sys/fs/cgroup</filename> and
  84                 <filename>/run</filename>. All of these are virtual
  85                 file systems, hence the runtime cost of the accesses
  86                 is relatively cheap.</para>
  87
  88                 <para>It is possible (and often a very good choice) to
  89                 mix calls to the synchronous interface of
  90                 <filename>sd-login.h</filename> with the asynchronous
  91                 D-Bus interface of systemd-logind. However, if this is
  92                 done you need to think a bit about possible races
  93                 since the stream of events from D-Bus and from
  94                 <filename>sd-login.h</filename> interfaces such as the
  95                 login monitor are asynchronous and not ordered against
  96                 each other.</para>
  97
  98                 <para>If the functions return string arrays, these are
  99                 generally <constant>NULL</constant> terminated and need to be freed by the
 100                 caller with the libc
 101                 <citerefentry><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 102                 call after use, including the strings referenced
 103                 therein. Similarly, individual strings returned need to
 104                 be freed, as well.</para>
 105
 106                 <para>As a special exception, instead of an empty
 107                 string array <constant>NULL</constant> may be returned, which should be
 108                 treated equivalent to an empty string array.</para>
 109
 110                 <para>See
 111                 <citerefentry><refentrytitle>sd_pid_get_session</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 112                 <citerefentry><refentrytitle>sd_uid_get_state</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 113                 <citerefentry><refentrytitle>sd_session_is_active</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 114                 <citerefentry><refentrytitle>sd_seat_get_active</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 115                 <citerefentry><refentrytitle>sd_get_seats</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 116                 <citerefentry><refentrytitle>sd_login_monitor_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 117                 for more information about the functions
 118                 implemented.</para>
 119         </refsect1>
 120
 121         <xi:include href="libsystemd-pkgconfig.xml" />
 122
 123         <refsect1>
 124                 <title>See Also</title>
 125                 <para>
 126                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 127                         <citerefentry><refentrytitle>sd_pid_get_session</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 128                         <citerefentry><refentrytitle>sd_uid_get_state</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 129                         <citerefentry><refentrytitle>sd_session_is_active</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 130                         <citerefentry><refentrytitle>sd_seat_get_active</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 131                         <citerefentry><refentrytitle>sd_get_seats</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 132                         <citerefentry><refentrytitle>sd_login_monitor_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 133                         <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 134                         <citerefentry><refentrytitle>sd-readahead</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 135                         <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 136                 </para>
 137         </refsect1>
 138
 139 </refentry>