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-or-later -->
5
6<refentry id="sd_seat_get_active" conditional='HAVE_PAM'
7          xmlns:xi="http://www.w3.org/2001/XInclude">
8
9  <refentryinfo>
10    <title>sd_seat_get_active</title>
11    <productname>systemd</productname>
12  </refentryinfo>
13
14  <refmeta>
15    <refentrytitle>sd_seat_get_active</refentrytitle>
16    <manvolnum>3</manvolnum>
17  </refmeta>
18
19  <refnamediv>
20    <refname>sd_seat_get_active</refname>
21    <refname>sd_seat_get_sessions</refname>
22    <refname>sd_seat_can_tty</refname>
23    <refname>sd_seat_can_graphical</refname>
24    <refpurpose>Determine state of a specific seat</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_seat_get_active</function></funcdef>
33        <paramdef>const char *<parameter>seat</parameter></paramdef>
34        <paramdef>char **<parameter>session</parameter></paramdef>
35        <paramdef>uid_t *<parameter>uid</parameter></paramdef>
36      </funcprototype>
37
38      <funcprototype>
39        <funcdef>int <function>sd_seat_get_sessions</function></funcdef>
40        <paramdef>const char *<parameter>seat</parameter></paramdef>
41        <paramdef>char ***<parameter>ret_sessions</parameter></paramdef>
42        <paramdef>uid_t **<parameter>ret_uids</parameter></paramdef>
43        <paramdef>unsigned int *<parameter>ret_n_uids</parameter></paramdef>
44      </funcprototype>
45
46      <funcprototype>
47        <funcdef>int <function>sd_seat_can_tty</function></funcdef>
48        <paramdef>const char *<parameter>seat</parameter></paramdef>
49      </funcprototype>
50
51      <funcprototype>
52        <funcdef>int <function>sd_seat_can_graphical</function></funcdef>
53        <paramdef>const char *<parameter>seat</parameter></paramdef>
54      </funcprototype>
55    </funcsynopsis>
56  </refsynopsisdiv>
57
58  <refsect1>
59    <title>Description</title>
60
61    <para><function>sd_seat_get_active()</function> may be used to
62    determine which session is currently active on a seat, if there is
63    any. Returns the session identifier and the user identifier of the
64    Unix user the session is belonging to. Either the session or the
65    user identifier parameter can be passed <constant>NULL</constant>,
66    in case only one of the parameters shall be queried. The returned
67    string needs to be freed with the libc
68    <citerefentry project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
69    call after use.</para>
70
71    <para><function>sd_seat_get_sessions()</function> may be used to determine all sessions on the specified
72    seat. Returns two arrays, one (<constant>NULL</constant> terminated) with the session identifiers of the
73    sessions and one with the user identifiers of the Unix users the sessions belong to. An additional
74    parameter may be used to return the number of entries in the latter array. This value is the same as the
75    return value if the return value is nonnegative. The output parameters may be passed as
76    <constant>NULL</constant> in case these output values are not needed. The arrays and the strings
77    referenced by them need to be freed with the libc <citerefentry
78    project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry> call after
79    use. Note that instead of an empty array <constant>NULL</constant> may be returned and should be
80    considered equivalent to an empty array.</para>
81
82    <para><function>sd_seat_can_tty()</function> may be used to
83    determine whether a specific seat provides TTY functionality, i.e.
84    is useful as a text console.</para>
85
86    <para><function>sd_seat_can_graphical()</function> may be used to
87    determine whether a specific seat provides graphics functionality,
88    i.e. is useful as a graphics display.</para>
89
90    <para>If the <varname>seat</varname> parameter of any of these
91    functions is passed as <constant>NULL</constant>, the operation is
92    executed for the seat of the session of the calling process, if
93    there is any.</para>
94  </refsect1>
95
96  <refsect1>
97    <title>Return Value</title>
98
99    <para> On success, <function>sd_seat_get_active()</function> returns 0 or a positive integer. On success,
100    <function>sd_seat_get_sessions()</function> returns the number of entries in the session identifier
101    array. If the test succeeds,
102    <function>sd_seat_can_tty()</function> and <function>sd_seat_can_graphical()</function> return a positive
103    integer, if it fails 0. On failure, these calls return a negative errno-style error code.</para>
104
105    <refsect2>
106      <title>Errors</title>
107
108      <para>Returned errors may indicate the following problems:</para>
109
110      <variablelist>
111
112        <varlistentry>
113          <term><constant>-ENODATA</constant></term>
114
115          <listitem><para>The given field is not specified for the described seat.</para>
116          </listitem>
117        </varlistentry>
118
119        <varlistentry>
120          <term><constant>-ENXIO</constant></term>
121
122          <listitem><para>The specified seat is unknown.</para>
123          </listitem>
124        </varlistentry>
125
126        <varlistentry>
127          <term><constant>-EINVAL</constant></term>
128
129          <listitem><para>An input parameter was invalid (out of range, or <constant>NULL</constant>, where
130          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    </refsect2>
140  </refsect1>
141
142  <xi:include href="libsystemd-pkgconfig.xml" />
143
144  <refsect1>
145    <title>History</title>
146
147    <para>In the past, <function>sd_seat_can_multi_session()</function> was used to check whether the seat
148    supports multiple sessions. All seats support that now, so that function has been deprecated and always
149    returns true.</para>
150  </refsect1>
151
152  <refsect1>
153    <title>See Also</title>
154
155    <para>
156      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
157      <citerefentry><refentrytitle>sd-login</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
158      <citerefentry><refentrytitle>sd_session_get_seat</refentrytitle><manvolnum>3</manvolnum></citerefentry>
159    </para>
160  </refsect1>
161
162</refentry>
163