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   This file is part of systemd.
   9
  10   Copyright 2010 Lennart Poettering
  11 -->
  12
  13 <refentry id="sd_get_seats" conditional='HAVE_PAM'>
  14
  15   <refentryinfo>
  16     <title>sd_get_seats</title>
  17     <productname>systemd</productname>
  18
  19     <authorgroup>
  20       <author>
  21         <contrib>Developer</contrib>
  22         <firstname>Lennart</firstname>
  23         <surname>Poettering</surname>
  24         <email>lennart@poettering.net</email>
  25       </author>
  26     </authorgroup>
  27   </refentryinfo>
  28
  29   <refmeta>
  30     <refentrytitle>sd_get_seats</refentrytitle>
  31     <manvolnum>3</manvolnum>
  32   </refmeta>
  33
  34   <refnamediv>
  35     <refname>sd_get_seats</refname>
  36     <refname>sd_get_sessions</refname>
  37     <refname>sd_get_uids</refname>
  38     <refname>sd_get_machine_names</refname>
  39     <refpurpose>Determine available seats, sessions, logged in users and virtual machines/containers</refpurpose>
  40   </refnamediv>
  41
  42   <refsynopsisdiv>
  43     <funcsynopsis>
  44       <funcsynopsisinfo>#include &lt;systemd/sd-login.h&gt;</funcsynopsisinfo>
  45
  46       <funcprototype>
  47         <funcdef>int <function>sd_get_seats</function></funcdef>
  48         <paramdef>char ***<parameter>seats</parameter></paramdef>
  49       </funcprototype>
  50
  51       <funcprototype>
  52         <funcdef>int <function>sd_get_sessions</function></funcdef>
  53         <paramdef>char ***<parameter>sessions</parameter></paramdef>
  54       </funcprototype>
  55
  56       <funcprototype>
  57         <funcdef>int <function>sd_get_uids</function></funcdef>
  58         <paramdef>uid_t **<parameter>users</parameter></paramdef>
  59       </funcprototype>
  60
  61       <funcprototype>
  62         <funcdef>int <function>sd_get_machine_names</function></funcdef>
  63         <paramdef>char ***<parameter>machines</parameter></paramdef>
  64       </funcprototype>
  65
  66     </funcsynopsis>
  67   </refsynopsisdiv>
  68
  69   <refsect1>
  70     <title>Description</title>
  71
  72     <para><function>sd_get_seats()</function> may be used to determine
  73     all currently available local seats. Returns the number of seat
  74     identifiers and if the input pointer is non-NULL, a
  75     <constant>NULL</constant>-terminated array of seat identifiers
  76     is stored at the address.
  77     The returned array and all strings it references need to be freed
  78     with the libc
  79     <citerefentry project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  80     call after use. Note that instead of an empty array
  81     <constant>NULL</constant> may be returned and should be considered
  82     equivalent to an empty array.</para>
  83
  84     <para>Similarly, <function>sd_get_sessions()</function> may be
  85     used to determine all current login sessions.</para>
  86
  87     <para>Similarly, <function>sd_get_uids()</function> may be used to
  88     determine all Unix users who currently have login sessions.</para>
  89
  90     <para>Similarly, <function>sd_get_machine_names()</function> may
  91     be used to determine all current virtual machines and containers
  92     on the system.</para>
  93
  94     <para>Note that the returned lists are not sorted and in an
  95     undefined order.</para>
  96   </refsect1>
  97
  98   <refsect1>
  99     <title>Return Value</title>
 100
 101     <para>On success, <function>sd_get_seats()</function>,
 102     <function>sd_get_sessions()</function>,
 103     <function>sd_get_uids()</function> and
 104     <function>sd_get_machine_names()</function> return the number of
 105     entries in the arrays. On failure, these calls return a negative
 106     errno-style error code.</para>
 107   </refsect1>
 108
 109   <refsect1>
 110     <title>Errors</title>
 111
 112     <para>Returned errors may indicate the following problems:</para>
 113
 114     <variablelist>
 115
 116       <varlistentry>
 117         <term><constant>-ENOMEM</constant></term>
 118
 119         <listitem><para>Memory allocation failed.</para></listitem>
 120       </varlistentry>
 121     </variablelist>
 122   </refsect1>
 123
 124   <refsect1>
 125     <title>Notes</title>
 126
 127     <para>The <function>sd_get_seats()</function>,
 128     <function>sd_get_sessions()</function>,
 129     <function>sd_get_uids()</function> and
 130     <function>sd_get_machine_names()</function> interfaces are
 131     available as a shared library, which can be compiled and linked to
 132     with the
 133     <constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 134     file.</para>
 135   </refsect1>
 136
 137   <refsect1>
 138     <title>See Also</title>
 139
 140     <para>
 141       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 142       <citerefentry><refentrytitle>sd-login</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 143       <citerefentry><refentrytitle>sd_session_get_seat</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 144     </para>
 145   </refsect1>
 146
 147 </refentry>