man/sd_seat_get_active.xml

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  10   Copyright 2010 Lennart Poettering
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  25
  26 <refentry id="sd_seat_get_active" conditional='HAVE_PAM'>
  27
  28   <refentryinfo>
  29     <title>sd_seat_get_active</title>
  30     <productname>systemd</productname>
  31
  32     <authorgroup>
  33       <author>
  34         <contrib>Developer</contrib>
  35         <firstname>Lennart</firstname>
  36         <surname>Poettering</surname>
  37         <email>lennart@poettering.net</email>
  38       </author>
  39     </authorgroup>
  40   </refentryinfo>
  41
  42   <refmeta>
  43     <refentrytitle>sd_seat_get_active</refentrytitle>
  44     <manvolnum>3</manvolnum>
  45   </refmeta>
  46
  47   <refnamediv>
  48     <refname>sd_seat_get_active</refname>
  49     <refname>sd_seat_get_sessions</refname>
  50     <refname>sd_seat_can_multi_session</refname>
  51     <refname>sd_seat_can_tty</refname>
  52     <refname>sd_seat_can_graphical</refname>
  53     <refpurpose>Determine state of a specific seat</refpurpose>
  54   </refnamediv>
  55
  56   <refsynopsisdiv>
  57     <funcsynopsis>
  58       <funcsynopsisinfo>#include &lt;systemd/sd-login.h&gt;</funcsynopsisinfo>
  59
  60       <funcprototype>
  61         <funcdef>int <function>sd_seat_get_active</function></funcdef>
  62         <paramdef>const char *<parameter>seat</parameter></paramdef>
  63         <paramdef>char **<parameter>session</parameter></paramdef>
  64         <paramdef>uid_t *<parameter>uid</parameter></paramdef>
  65       </funcprototype>
  66
  67       <funcprototype>
  68         <funcdef>int <function>sd_seat_get_sessions</function></funcdef>
  69         <paramdef>const char *<parameter>seat</parameter></paramdef>
  70         <paramdef>char ***<parameter>sessions</parameter></paramdef>
  71         <paramdef>uid_t **<parameter>uid</parameter></paramdef>
  72         <paramdef>unsigned int *<parameter>n_uids</parameter></paramdef>
  73       </funcprototype>
  74
  75       <funcprototype>
  76         <funcdef>int <function>sd_seat_can_multi_session</function></funcdef>
  77         <paramdef>const char *<parameter>seat</parameter></paramdef>
  78       </funcprototype>
  79
  80       <funcprototype>
  81         <funcdef>int <function>sd_seat_can_tty</function></funcdef>
  82         <paramdef>const char *<parameter>seat</parameter></paramdef>
  83       </funcprototype>
  84
  85       <funcprototype>
  86         <funcdef>int <function>sd_seat_can_graphical</function></funcdef>
  87         <paramdef>const char *<parameter>seat</parameter></paramdef>
  88       </funcprototype>
  89     </funcsynopsis>
  90   </refsynopsisdiv>
  91
  92   <refsect1>
  93     <title>Description</title>
  94
  95     <para><function>sd_seat_get_active()</function> may be used to
  96     determine which session is currently active on a seat, if there is
  97     any. Returns the session identifier and the user identifier of the
  98     Unix user the session is belonging to. Either the session or the
  99     user identifier parameter can be passed <constant>NULL</constant>,
 100     in case only one of the parameters shall be queried. The returned
 101     string needs to be freed with the libc
 102     <citerefentry project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 103     call after use.</para>
 104
 105     <para><function>sd_seat_get_sessions()</function> may be used to
 106     determine all sessions on the specified seat. Returns two arrays,
 107     one (<constant>NULL</constant> terminated) with the session
 108     identifiers of the sessions and one with the user identifiers of
 109     the Unix users the sessions belong to. An additional parameter may
 110     be used to return the number of entries in the latter array. This
 111     value is the same the return value, if the latter is nonnegative.
 112     The two arrays and the last parameter may be passed as
 113     <constant>NULL</constant> in case these values need not to be
 114     determined. The arrays and the strings referenced by them need to
 115     be freed with the libc
 116     <citerefentry project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 117     call after use. Note that instead of an empty array
 118     <constant>NULL</constant> may be returned and should be considered
 119     equivalent to an empty array.</para>
 120
 121     <para><function>sd_seat_can_multi_session()</function> may be used
 122     to determine whether a specific seat is capable of multi-session,
 123     i.e. allows multiple login sessions in parallel (with only one
 124     being active at a time).</para>
 125
 126     <para><function>sd_seat_can_tty()</function> may be used to
 127     determine whether a specific seat provides TTY functionality, i.e.
 128     is useful as a text console.</para>
 129
 130     <para><function>sd_seat_can_graphical()</function> may be used to
 131     determine whether a specific seat provides graphics functionality,
 132     i.e. is useful as a graphics display.</para>
 133
 134     <para>If the <varname>seat</varname> parameter of any of these
 135     functions is passed as <constant>NULL</constant>, the operation is
 136     executed for the seat of the session of the calling process, if
 137     there is any.</para>
 138   </refsect1>
 139
 140   <refsect1>
 141     <title>Return Value</title>
 142
 143     <para> On success, <function>sd_seat_get_active()</function>
 144     returns 0 or a positive integer. On success,
 145     <function>sd_seat_get_sessions()</function> returns the number of
 146     entries in the session identifier array. If the test succeeds,
 147     <function>sd_seat_can_multi_session</function>,
 148     <function>sd_seat_can_tty</function> and
 149     <function>sd_seat_can_graphical</function> return a positive
 150     integer, if it fails 0. On failure, these calls return a negative
 151     errno-style error code.</para>
 152   </refsect1>
 153
 154   <refsect1>
 155     <title>Errors</title>
 156
 157     <para>Returned errors may indicate the following problems:</para>
 158
 159     <variablelist>
 160
 161       <varlistentry>
 162         <term><constant>-ENODATA</constant></term>
 163
 164         <listitem><para>The given field is not specified for the described
 165         seat.</para>
 166         </listitem>
 167       </varlistentry>
 168
 169       <varlistentry>
 170         <term><constant>-ENXIO</constant></term>
 171
 172         <listitem><para>The specified seat is unknown.</para>
 173         </listitem>
 174       </varlistentry>
 175
 176       <varlistentry>
 177         <term><constant>-EINVAL</constant></term>
 178
 179         <listitem><para>An input parameter was invalid (out of range,
 180         or NULL, where that is not accepted).</para></listitem>
 181       </varlistentry>
 182
 183       <varlistentry>
 184         <term><constant>-ENOMEM</constant></term>
 185
 186         <listitem><para>Memory allocation failed.</para></listitem>
 187       </varlistentry>
 188     </variablelist>
 189   </refsect1>
 190
 191   <refsect1>
 192     <title>Notes</title>
 193
 194     <para>The <function>sd_seat_get_active()</function>,
 195     <function>sd_seat_get_sessions()</function>,
 196     <function>sd_seat_can_multi_session()</function>,
 197     <function>sd_seat_can_tty()</function> and
 198     <function>sd_seat_can_graphical()</function> interfaces are
 199     available as a shared library, which can be compiled and linked to
 200     with the
 201     <constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 202     file.</para>
 203   </refsect1>
 204
 205   <refsect1>
 206     <title>See Also</title>
 207
 208     <para>
 209       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 210       <citerefentry><refentrytitle>sd-login</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 211       <citerefentry><refentrytitle>sd_session_get_seat</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 212     </para>
 213   </refsect1>
 214
 215 </refentry>