man/sd_seat_get_active.xml

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   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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  23
  24 <refentry id="sd_seat_get_active" conditional='HAVE_PAM'>
  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                 <refname>sd_seat_can_tty</refname>
  50                 <refname>sd_seat_can_graphical</refname>
  51                 <refpurpose>Determine state of a specific seat</refpurpose>
  52         </refnamediv>
  53
  54         <refsynopsisdiv>
  55                 <funcsynopsis>
  56                         <funcsynopsisinfo>#include &lt;systemd/sd-login.h&gt;</funcsynopsisinfo>
  57
  58                         <funcprototype>
  59                                 <funcdef>int <function>sd_seat_get_active</function></funcdef>
  60                                 <paramdef>const char* <parameter>seat</parameter></paramdef>
  61                                 <paramdef>char** <parameter>session</parameter></paramdef>
  62                                 <paramdef>uid_t* <parameter>uid</parameter></paramdef>
  63                         </funcprototype>
  64
  65                         <funcprototype>
  66                                 <funcdef>int <function>sd_seat_get_sessions</function></funcdef>
  67                                 <paramdef>const char* <parameter>seat</parameter></paramdef>
  68                                 <paramdef>char*** <parameter>sessions</parameter></paramdef>
  69                                 <paramdef>uid_t** <parameter>uid</parameter></paramdef>
  70                                 <paramdef>unsigned int* <parameter>n_uids</parameter></paramdef>
  71                         </funcprototype>
  72
  73                         <funcprototype>
  74                                 <funcdef>int <function>sd_seat_can_multi_session</function></funcdef>
  75                                 <paramdef>const char* <parameter>seat</parameter></paramdef>
  76                         </funcprototype>
  77
  78                         <funcprototype>
  79                                 <funcdef>int <function>sd_seat_can_tty</function></funcdef>
  80                                 <paramdef>const char* <parameter>seat</parameter></paramdef>
  81                         </funcprototype>
  82
  83                         <funcprototype>
  84                                 <funcdef>int <function>sd_seat_can_graphical</function></funcdef>
  85                                 <paramdef>const char* <parameter>seat</parameter></paramdef>
  86                         </funcprototype>
  87                 </funcsynopsis>
  88         </refsynopsisdiv>
  89
  90         <refsect1>
  91                 <title>Description</title>
  92
  93                 <para><function>sd_seat_get_active()</function> may be
  94                 used to determine which session is currently active on
  95                 a seat, if there is any. Returns the session
  96                 identifier and the user identifier of the Unix user
  97                 the session is belonging to. Either the session or the
  98                 user identifier parameter can be passed
  99                 <constant>NULL</constant>, in case only one of the
 100                 parameters shall be queried. The returned string needs
 101                 to be freed with the libc
 102                 <citerefentry><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 103                 call after use.</para>
 104
 105                 <para><function>sd_seat_get_sessions()</function> may
 106                 be used to determine all sessions on the specified
 107                 seat. Returns two arrays, one (<constant>NULL</constant> terminated) with
 108                 the session identifiers of the sessions and one with
 109                 the user identifiers of the Unix users the sessions
 110                 belong to. An additional parameter may be used to
 111                 return the number of entries in the latter array. The
 112                 two arrays and the latter parameter may be passed as
 113                 <constant>NULL</constant> in case these values need not to be
 114                 determined. The arrays and the strings referenced by
 115                 them need to be freed with the libc
 116                 <citerefentry><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 117                 call after use. Note that instead of an empty array
 118                 <constant>NULL</constant> may be returned and should be considered
 119                 equivalent to an empty array.</para>
 120
 121                 <para><function>sd_seat_can_multi_session()</function>
 122                 may be used to determine whether a specific seat is
 123                 capable of multi-session, i.e. allows multiple login
 124                 sessions in parallel (with only one being active at a
 125                 time).</para>
 126
 127                 <para><function>sd_seat_can_tty()</function> may be
 128                 used to determine whether a specific seat provides TTY
 129                 functionality, i.e. is useful as a text console.</para>
 130
 131                 <para><function>sd_seat_can_graphical()</function> may
 132                 be used to determine whether a specific seat provides
 133                 graphics functionality, i.e. is useful as a graphics
 134                 display.</para>
 135
 136                 <para>If the <varname>seat</varname> parameter of any
 137                 of these functions is passed as
 138                 <constant>NULL</constant>, the operation is executed
 139                 for the seat of the session of the calling process, if
 140                 there is any.</para>
 141         </refsect1>
 142
 143         <refsect1>
 144                 <title>Return Value</title>
 145
 146                 <para> On success
 147                 <function>sd_seat_get_active()</function>
 148                 returns 0 or a positive integer. On success
 149                 <function>sd_seat_get_sessions()</function> returns
 150                 the number of entries in the session identifier
 151                 array. If the test succeeds,
 152                 <function>sd_seat_can_multi_session</function>,
 153                 <function>sd_seat_can_tty</function> and
 154                 <function>sd_seat_can_graphical</function> return a
 155                 positive integer, if it fails 0. On failure, these
 156                 calls return a negative errno-style error code.</para>
 157         </refsect1>
 158
 159         <refsect1>
 160                 <title>Notes</title>
 161
 162                 <para>The <function>sd_seat_get_active()</function>,
 163                 <function>sd_seat_get_sessions()</function>,
 164                 <function>sd_seat_can_multi_session()</function>,
 165                 <function>sd_seat_can_tty()</function> and
 166                 <function>sd_seat_can_grapical()</function> interfaces
 167                 are available as a shared library, which can be compiled
 168                 and linked to with the
 169                 <constant>libsystemd-login</constant> <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 170                 file.</para>
 171         </refsect1>
 172
 173         <refsect1>
 174                 <title>See Also</title>
 175
 176                 <para>
 177                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 178                         <citerefentry><refentrytitle>sd-login</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 179                         <citerefentry><refentrytitle>sd_session_get_seat</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 180                 </para>
 181         </refsect1>
 182
 183 </refentry>