man/sd_get_seats.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   SPDX-License-Identifier: LGPL-2.1+
   7 -->
   8
   9 <refentry id="sd_get_seats" conditional='HAVE_PAM'
  10           xmlns:xi="http://www.w3.org/2001/XInclude">
  11
  12   <refentryinfo>
  13     <title>sd_get_seats</title>
  14     <productname>systemd</productname>
  15   </refentryinfo>
  16
  17   <refmeta>
  18     <refentrytitle>sd_get_seats</refentrytitle>
  19     <manvolnum>3</manvolnum>
  20   </refmeta>
  21
  22   <refnamediv>
  23     <refname>sd_get_seats</refname>
  24     <refname>sd_get_sessions</refname>
  25     <refname>sd_get_uids</refname>
  26     <refname>sd_get_machine_names</refname>
  27     <refpurpose>Determine available seats, sessions, logged in users and virtual machines/containers</refpurpose>
  28   </refnamediv>
  29
  30   <refsynopsisdiv>
  31     <funcsynopsis>
  32       <funcsynopsisinfo>#include &lt;systemd/sd-login.h&gt;</funcsynopsisinfo>
  33
  34       <funcprototype>
  35         <funcdef>int <function>sd_get_seats</function></funcdef>
  36         <paramdef>char ***<parameter>seats</parameter></paramdef>
  37       </funcprototype>
  38
  39       <funcprototype>
  40         <funcdef>int <function>sd_get_sessions</function></funcdef>
  41         <paramdef>char ***<parameter>sessions</parameter></paramdef>
  42       </funcprototype>
  43
  44       <funcprototype>
  45         <funcdef>int <function>sd_get_uids</function></funcdef>
  46         <paramdef>uid_t **<parameter>users</parameter></paramdef>
  47       </funcprototype>
  48
  49       <funcprototype>
  50         <funcdef>int <function>sd_get_machine_names</function></funcdef>
  51         <paramdef>char ***<parameter>machines</parameter></paramdef>
  52       </funcprototype>
  53
  54     </funcsynopsis>
  55   </refsynopsisdiv>
  56
  57   <refsect1>
  58     <title>Description</title>
  59
  60     <para><function>sd_get_seats()</function> may be used to determine
  61     all currently available local seats. Returns the number of seat
  62     identifiers and if the input pointer is non-NULL, a
  63     <constant>NULL</constant>-terminated array of seat identifiers
  64     is stored at the address.
  65     The returned array and all strings it references need to be freed
  66     with the libc
  67     <citerefentry project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  68     call after use. Note that instead of an empty array
  69     <constant>NULL</constant> may be returned and should be considered
  70     equivalent to an empty array.</para>
  71
  72     <para>Similarly, <function>sd_get_sessions()</function> may be
  73     used to determine all current login sessions.</para>
  74
  75     <para>Similarly, <function>sd_get_uids()</function> may be used to
  76     determine all Unix users who currently have login sessions.</para>
  77
  78     <para>Similarly, <function>sd_get_machine_names()</function> may
  79     be used to determine all current virtual machines and containers
  80     on the system.</para>
  81
  82     <para>Note that the returned lists are not sorted and in an
  83     undefined order.</para>
  84   </refsect1>
  85
  86   <refsect1>
  87     <title>Return Value</title>
  88
  89     <para>On success, <function>sd_get_seats()</function>,
  90     <function>sd_get_sessions()</function>,
  91     <function>sd_get_uids()</function> and
  92     <function>sd_get_machine_names()</function> return the number of
  93     entries in the arrays. On failure, these calls return a negative
  94     errno-style error code.</para>
  95   </refsect1>
  96
  97   <refsect1>
  98     <title>Errors</title>
  99
 100     <para>Returned errors may indicate the following problems:</para>
 101
 102     <variablelist>
 103
 104       <varlistentry>
 105         <term><constant>-ENOMEM</constant></term>
 106
 107         <listitem><para>Memory allocation failed.</para></listitem>
 108       </varlistentry>
 109     </variablelist>
 110   </refsect1>
 111
 112   <xi:include href="libsystemd-pkgconfig.xml" />
 113
 114   <refsect1>
 115     <title>See Also</title>
 116
 117     <para>
 118       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 119       <citerefentry><refentrytitle>sd-login</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 120       <citerefentry><refentrytitle>sd_session_get_seat</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 121     </para>
 122   </refsect1>
 123
 124 </refentry>