man/sd_seat_get_active.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
   5
   6 <refentry id="sd_seat_get_active" conditional='HAVE_PAM'
   7           xmlns:xi="http://www.w3.org/2001/XInclude">
   8
   9   <refentryinfo>
  10     <title>sd_seat_get_active</title>
  11     <productname>systemd</productname>
  12   </refentryinfo>
  13
  14   <refmeta>
  15     <refentrytitle>sd_seat_get_active</refentrytitle>
  16     <manvolnum>3</manvolnum>
  17   </refmeta>
  18
  19   <refnamediv>
  20     <refname>sd_seat_get_active</refname>
  21     <refname>sd_seat_get_sessions</refname>
  22     <refname>sd_seat_can_tty</refname>
  23     <refname>sd_seat_can_graphical</refname>
  24     <refpurpose>Determine state of a specific seat</refpurpose>
  25   </refnamediv>
  26
  27   <refsynopsisdiv>
  28     <funcsynopsis>
  29       <funcsynopsisinfo>#include &lt;systemd/sd-login.h&gt;</funcsynopsisinfo>
  30
  31       <funcprototype>
  32         <funcdef>int <function>sd_seat_get_active</function></funcdef>
  33         <paramdef>const char *<parameter>seat</parameter></paramdef>
  34         <paramdef>char **<parameter>session</parameter></paramdef>
  35         <paramdef>uid_t *<parameter>uid</parameter></paramdef>
  36       </funcprototype>
  37
  38       <funcprototype>
  39         <funcdef>int <function>sd_seat_get_sessions</function></funcdef>
  40         <paramdef>const char *<parameter>seat</parameter></paramdef>
  41         <paramdef>char ***<parameter>ret_sessions</parameter></paramdef>
  42         <paramdef>uid_t **<parameter>ret_uids</parameter></paramdef>
  43         <paramdef>unsigned int *<parameter>ret_n_uids</parameter></paramdef>
  44       </funcprototype>
  45
  46       <funcprototype>
  47         <funcdef>int <function>sd_seat_can_tty</function></funcdef>
  48         <paramdef>const char *<parameter>seat</parameter></paramdef>
  49       </funcprototype>
  50
  51       <funcprototype>
  52         <funcdef>int <function>sd_seat_can_graphical</function></funcdef>
  53         <paramdef>const char *<parameter>seat</parameter></paramdef>
  54       </funcprototype>
  55     </funcsynopsis>
  56   </refsynopsisdiv>
  57
  58   <refsect1>
  59     <title>Description</title>
  60
  61     <para><function>sd_seat_get_active()</function> may be used to
  62     determine which session is currently active on a seat, if there is
  63     any. Returns the session identifier and the user identifier of the
  64     Unix user the session is belonging to. Either the session or the
  65     user identifier parameter can be passed <constant>NULL</constant>,
  66     in case only one of the parameters shall be queried. The returned
  67     string needs to be freed with the libc
  68     <citerefentry project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  69     call after use.</para>
  70
  71     <para><function>sd_seat_get_sessions()</function> may be used to determine all sessions on the specified
  72     seat. Returns two arrays, one (<constant>NULL</constant> terminated) with the session identifiers of the
  73     sessions and one with the user identifiers of the Unix users the sessions belong to. An additional
  74     parameter may be used to return the number of entries in the latter array. This value is the same as the
  75     return value if the return value is nonnegative. The output parameters may be passed as
  76     <constant>NULL</constant> in case these output values are not needed. The arrays and the strings
  77     referenced by them need to be freed with the libc <citerefentry
  78     project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry> call after
  79     use. Note that instead of an empty array <constant>NULL</constant> may be returned and should be
  80     considered equivalent to an empty array.</para>
  81
  82     <para><function>sd_seat_can_tty()</function> may be used to
  83     determine whether a specific seat provides TTY functionality, i.e.
  84     is useful as a text console.</para>
  85
  86     <para><function>sd_seat_can_graphical()</function> may be used to
  87     determine whether a specific seat provides graphics functionality,
  88     i.e. is useful as a graphics display.</para>
  89
  90     <para>If the <varname>seat</varname> parameter of any of these
  91     functions is passed as <constant>NULL</constant>, the operation is
  92     executed for the seat of the session of the calling process, if
  93     there is any.</para>
  94   </refsect1>
  95
  96   <refsect1>
  97     <title>Return Value</title>
  98
  99     <para> On success, <function>sd_seat_get_active()</function> returns 0 or a positive integer. On success,
 100     <function>sd_seat_get_sessions()</function> returns the number of entries in the session identifier
 101     array. If the test succeeds,
 102     <function>sd_seat_can_tty</function> and <function>sd_seat_can_graphical</function> return a positive
 103     integer, if it fails 0. On failure, these calls return a negative errno-style error code.</para>
 104
 105     <refsect2>
 106       <title>Errors</title>
 107
 108       <para>Returned errors may indicate the following problems:</para>
 109
 110       <variablelist>
 111
 112         <varlistentry>
 113           <term><constant>-ENODATA</constant></term>
 114
 115           <listitem><para>The given field is not specified for the described seat.</para>
 116           </listitem>
 117         </varlistentry>
 118
 119         <varlistentry>
 120           <term><constant>-ENXIO</constant></term>
 121
 122           <listitem><para>The specified seat is unknown.</para>
 123           </listitem>
 124         </varlistentry>
 125
 126         <varlistentry>
 127           <term><constant>-EINVAL</constant></term>
 128
 129           <listitem><para>An input parameter was invalid (out of range, or <constant>NULL</constant>, where
 130           that is not accepted).</para></listitem>
 131         </varlistentry>
 132
 133         <varlistentry>
 134           <term><constant>-ENOMEM</constant></term>
 135
 136           <listitem><para>Memory allocation failed.</para></listitem>
 137         </varlistentry>
 138       </variablelist>
 139     </refsect2>
 140   </refsect1>
 141
 142   <xi:include href="libsystemd-pkgconfig.xml" />
 143
 144   <refsect1>
 145     <title>History</title>
 146
 147     <para>In the past, <function>sd_seat_can_multi_session()</function> was used to check whether the seat
 148     supports multiple sessions. All seats support that now, so that function has been deprecated and always
 149     returns true.</para>
 150   </refsect1>
 151
 152   <refsect1>
 153     <title>See Also</title>
 154
 155     <para>
 156       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 157       <citerefentry><refentrytitle>sd-login</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 158       <citerefentry><refentrytitle>sd_session_get_seat</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 159     </para>
 160   </refsect1>
 161
 162 </refentry>