man/sd_get_seats.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_get_seats" conditional='HAVE_PAM'
   7           xmlns:xi="http://www.w3.org/2001/XInclude">
   8
   9   <refentryinfo>
  10     <title>sd_get_seats</title>
  11     <productname>systemd</productname>
  12   </refentryinfo>
  13
  14   <refmeta>
  15     <refentrytitle>sd_get_seats</refentrytitle>
  16     <manvolnum>3</manvolnum>
  17   </refmeta>
  18
  19   <refnamediv>
  20     <refname>sd_get_seats</refname>
  21     <refname>sd_get_sessions</refname>
  22     <refname>sd_get_uids</refname>
  23     <refname>sd_get_machine_names</refname>
  24     <refpurpose>Determine available seats, sessions, logged in users and virtual machines/containers</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_get_seats</function></funcdef>
  33         <paramdef>char ***<parameter>seats</parameter></paramdef>
  34       </funcprototype>
  35
  36       <funcprototype>
  37         <funcdef>int <function>sd_get_sessions</function></funcdef>
  38         <paramdef>char ***<parameter>sessions</parameter></paramdef>
  39       </funcprototype>
  40
  41       <funcprototype>
  42         <funcdef>int <function>sd_get_uids</function></funcdef>
  43         <paramdef>uid_t **<parameter>users</parameter></paramdef>
  44       </funcprototype>
  45
  46       <funcprototype>
  47         <funcdef>int <function>sd_get_machine_names</function></funcdef>
  48         <paramdef>char ***<parameter>machines</parameter></paramdef>
  49       </funcprototype>
  50
  51     </funcsynopsis>
  52   </refsynopsisdiv>
  53
  54   <refsect1>
  55     <title>Description</title>
  56
  57     <para><function>sd_get_seats()</function> may be used to determine
  58     all currently available local seats. Returns the number of seat
  59     identifiers and if the input pointer is non-NULL, a
  60     <constant>NULL</constant>-terminated array of seat identifiers
  61     is stored at the address.
  62     The returned array and all strings it references need to be freed
  63     with the libc
  64     <citerefentry project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  65     call after use. Note that instead of an empty array
  66     <constant>NULL</constant> may be returned and should be considered
  67     equivalent to an empty array.</para>
  68
  69     <para>Similarly, <function>sd_get_sessions()</function> may be
  70     used to determine all current login sessions.</para>
  71
  72     <para>Similarly, <function>sd_get_uids()</function> may be used to
  73     determine all Unix users who currently have login sessions.</para>
  74
  75     <para>Similarly, <function>sd_get_machine_names()</function> may
  76     be used to determine all current virtual machines and containers
  77     on the system.</para>
  78
  79     <para>Note that the returned lists are not sorted and in an
  80     undefined order.</para>
  81   </refsect1>
  82
  83   <refsect1>
  84     <title>Return Value</title>
  85
  86     <para>On success, <function>sd_get_seats()</function>,
  87     <function>sd_get_sessions()</function>,
  88     <function>sd_get_uids()</function> and
  89     <function>sd_get_machine_names()</function> return the number of
  90     entries in the arrays. On failure, these calls return a negative
  91     errno-style error code.</para>
  92   </refsect1>
  93
  94   <refsect1>
  95     <title>Errors</title>
  96
  97     <para>Returned errors may indicate the following problems:</para>
  98
  99     <variablelist>
 100
 101       <varlistentry>
 102         <term><constant>-ENOMEM</constant></term>
 103
 104         <listitem><para>Memory allocation failed.</para></listitem>
 105       </varlistentry>
 106     </variablelist>
 107   </refsect1>
 108
 109   <xi:include href="libsystemd-pkgconfig.xml" />
 110
 111   <refsect1>
 112     <title>See Also</title>
 113
 114     <para>
 115       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 116       <citerefentry><refentrytitle>sd-login</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 117       <citerefentry><refentrytitle>sd_session_get_seat</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 118     </para>
 119   </refsect1>
 120
 121 </refentry>