man/sd_get_seats.xml

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   8   Copyright 2010 Lennart Poettering
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  23
  24 <refentry id="sd_get_seats" conditional='HAVE_PAM'>
  25
  26   <refentryinfo>
  27     <title>sd_get_seats</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_get_seats</refentrytitle>
  42     <manvolnum>3</manvolnum>
  43   </refmeta>
  44
  45   <refnamediv>
  46     <refname>sd_get_seats</refname>
  47     <refname>sd_get_sessions</refname>
  48     <refname>sd_get_uids</refname>
  49     <refname>sd_get_machine_names</refname>
  50     <refpurpose>Determine available seats, sessions, logged in users and virtual machines/containers</refpurpose>
  51   </refnamediv>
  52
  53   <refsynopsisdiv>
  54     <funcsynopsis>
  55       <funcsynopsisinfo>#include &lt;systemd/sd-login.h&gt;</funcsynopsisinfo>
  56
  57       <funcprototype>
  58         <funcdef>int <function>sd_get_seats</function></funcdef>
  59         <paramdef>char ***<parameter>seats</parameter></paramdef>
  60       </funcprototype>
  61
  62       <funcprototype>
  63         <funcdef>int <function>sd_get_sessions</function></funcdef>
  64         <paramdef>char ***<parameter>sessions</parameter></paramdef>
  65       </funcprototype>
  66
  67       <funcprototype>
  68         <funcdef>int <function>sd_get_uids</function></funcdef>
  69         <paramdef>uid_t **<parameter>users</parameter></paramdef>
  70       </funcprototype>
  71
  72       <funcprototype>
  73         <funcdef>int <function>sd_get_machine_names</function></funcdef>
  74         <paramdef>char ***<parameter>machines</parameter></paramdef>
  75       </funcprototype>
  76
  77     </funcsynopsis>
  78   </refsynopsisdiv>
  79
  80   <refsect1>
  81     <title>Description</title>
  82
  83     <para><function>sd_get_seats()</function> may be used to determine
  84     all currently available local seats. Returns a
  85     <constant>NULL</constant> terminated array of seat identifiers.
  86     The returned array and all strings it references need to be freed
  87     with the libc
  88     <citerefentry project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  89     call after use. Note that instead of an empty array
  90     <constant>NULL</constant> may be returned and should be considered
  91     equivalent to an empty array.</para>
  92
  93     <para>Similarly, <function>sd_get_sessions()</function> may be
  94     used to determine all current login sessions.</para>
  95
  96     <para>Similarly, <function>sd_get_uids()</function> may be used to
  97     determine all Unix users who currently have login sessions.</para>
  98
  99     <para>Similarly, <function>sd_get_machine_names()</function> may
 100     be used to determine all current virtual machines and containers
 101     on the system.</para>
 102
 103     <para>Note that the returned lists are not sorted and in an
 104     undefined order.</para>
 105   </refsect1>
 106
 107   <refsect1>
 108     <title>Return Value</title>
 109
 110     <para>On success, <function>sd_get_seats()</function>,
 111     <function>sd_get_sessions()</function>,
 112     <function>sd_get_uids()</function> and
 113     <function>sd_get_machine_names()</function> return the number of
 114     entries in the arrays. On failure, these calls return a negative
 115     errno-style error code.</para>
 116   </refsect1>
 117
 118
 119   <refsect1>
 120     <title>Errors</title>
 121
 122     <para>Returned errors may indicate the following problems:</para>
 123
 124     <variablelist>
 125
 126       <varlistentry>
 127         <term><constant>-EINVAL</constant></term>
 128
 129         <listitem><para>An input parameter was invalid (out of range,
 130         or NULL, where 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   </refsect1>
 140
 141   <refsect1>
 142     <title>Notes</title>
 143
 144     <para>The <function>sd_get_seats()</function>,
 145     <function>sd_get_sessions()</function>,
 146     <function>sd_get_uids()</function> and
 147     <function>sd_get_machine_names()</function> interfaces are
 148     available as a shared library, which can be compiled and linked to
 149     with the
 150     <constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 151     file.</para>
 152   </refsect1>
 153
 154   <refsect1>
 155     <title>See Also</title>
 156
 157     <para>
 158       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 159       <citerefentry><refentrytitle>sd-login</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 160       <citerefentry><refentrytitle>sd_session_get_seat</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 161     </para>
 162   </refsect1>
 163
 164 </refentry>