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">
  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                 <refpurpose>Determine state of a specific seat</refpurpose>
  50         </refnamediv>
  51
  52         <refsynopsisdiv>
  53                 <funcsynopsis>
  54                         <funcsynopsisinfo>#include &lt;systemd/sd-login.h&gt;</funcsynopsisinfo>
  55
  56                         <funcprototype>
  57                                 <funcdef>int <function>sd_seat_get_active</function></funcdef>
  58                                 <paramdef>const char* <parameter>seat</parameter></paramdef>
  59                                 <paramdef>char** <parameter>session</parameter></paramdef>
  60                                 <paramdef>uid_t* <parameter>uid</parameter></paramdef>
  61                         </funcprototype>
  62
  63                         <funcprototype>
  64                                 <funcdef>int <function>sd_seat_get_sessions</function></funcdef>
  65                                 <paramdef>const char* <parameter>seat</parameter></paramdef>
  66                                 <paramdef>char*** <parameter>sessions</parameter></paramdef>
  67                                 <paramdef>uid_t** <parameter>uid</parameter></paramdef>
  68                                 <paramdef>unsigned* <parameter>n_uids</parameter></paramdef>
  69                         </funcprototype>
  70
  71                         <funcprototype>
  72                                 <funcdef>int <function>sd_seat_can_multi_session</function></funcdef>
  73                                 <paramdef>const char* <parameter>seat</parameter></paramdef>
  74                         </funcprototype>
  75                 </funcsynopsis>
  76         </refsynopsisdiv>
  77
  78         <refsect1>
  79                 <title>Description</title>
  80
  81                 <para><function>sd_seat_get_active()</function> may be
  82                 used to determine which session is currently active on
  83                 a seat, if there is any. Returns the session
  84                 identifier and the user identifier of the Unix user
  85                 the session is belonging to. Either the session or the
  86                 user identifier parameter can be be passed NULL, in
  87                 case only one of the parameters shall be queried. The
  88                 returned string needs to be freed with the libc
  89                 <citerefentry><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  90                 call after use.</para>
  91
  92                 <para><function>sd_seat_get_sessions()</function> may
  93                 be used to determine all sessions on the specified
  94                 seat. Returns two arrays, one (NULL terminated) with
  95                 the session identifiers of the sessions and one with
  96                 the user identifiers of the Unix users the sessions
  97                 belong to. An additional parameter may be used to
  98                 return the number of entries in the latter array. The
  99                 two arrays and the latter parameter may be passed as
 100                 NULL in case these values need not to be
 101                 determined. The arrays and the strings referenced by
 102                 them need to be freed with the libc
 103                 <citerefentry><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 104                 call after use. Note that instead of an empty array
 105                 NULL may be returned and should be considered
 106                 equivalent to an empty array.</para>
 107
 108                 <para><function>sd_seat_can_multi_session()</function>
 109                 may be used to determine whether a specific seat is
 110                 capable of multi-session, i.e. allows multiple login
 111                 sessions in parallel (whith only one being active at a
 112                 time).</para>
 113
 114                 <para>If the <literal>seat</literal> parameter of any
 115                 of these functions is passed as NULL the operation is
 116                 executed for the seat of the session of the calling
 117                 process, if there is any.</para>
 118         </refsect1>
 119
 120         <refsect1>
 121                 <title>Return Value</title>
 122
 123                 <para> On success
 124                 <function>sd_seat_get_active()</function> return
 125                 return 0 or a positive integer. On success
 126                 <function>sd_seat_get_sessions()</function> returns
 127                 the number of entries in the session identifier
 128                 array. If the test succeeds
 129                 <function>sd_seat_can_multi_session</function> returns
 130                 a positive integer, if it fails 0. On failure, these
 131                 calls return a negative errno-style error code.</para>
 132         </refsect1>
 133
 134         <refsect1>
 135                 <title>Notes</title>
 136
 137                 <para>The <function>sd_seat_get_active()</function>,
 138                 <function>sd_seat_get_sessions()</function>, and
 139                 <function>sd_seat_can_multi_session()</function> interfaces
 140                 are available as shared library, which can be compiled
 141                 and linked to with the
 142                 <literal>libsystemd-login</literal>
 143                 <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 144                 file.</para>
 145         </refsect1>
 146
 147         <refsect1>
 148                 <title>See Also</title>
 149
 150                 <para>
 151                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 152                         <citerefentry><refentrytitle>sd-login</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 153                         <citerefentry><refentrytitle>sd_session_get_seat</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 154                 </para>
 155         </refsect1>
 156
 157 </refentry>