summaryrefslogtreecommitdiff
path: root/man/sd_bus_default.xml
blob: fbf10d019f7ecd504a2c95afb06644c079244c88 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">

<!--
  This file is part of systemd.

  Copyright 2014 Zbigniew Jędrzejewski-Szmek

  systemd is free software; you can redistribute it and/or modify it
  under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation; either version 2.1 of the License, or
  (at your option) any later version.

  systemd is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->

<refentry id="sd_bus_default">

  <refentryinfo>
    <title>sd_bus_default</title>
    <productname>systemd</productname>

    <authorgroup>
      <author>
        <contrib>A monkey with a typewriter</contrib>
        <firstname>Zbigniew</firstname>
        <surname>Jędrzejewski-Szmek</surname>
        <email>zbyszek@in.waw.pl</email>
      </author>
    </authorgroup>
  </refentryinfo>

  <refmeta>
    <refentrytitle>sd_bus_default</refentrytitle>
    <manvolnum>3</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>sd_bus_default</refname>
    <refname>sd_bus_default_user</refname>
    <refname>sd_bus_default_system</refname>

    <refname>sd_bus_open</refname>
    <refname>sd_bus_open_user</refname>
    <refname>sd_bus_open_system</refname>
    <refname>sd_bus_open_system_remote</refname>
    <refname>sd_bus_open_system_machine</refname>

    <refpurpose>Acquire a connection to a system or user bus</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <funcsynopsis>
      <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>

      <funcprototype>
        <funcdef>int <function>sd_bus_default</function></funcdef>
        <paramdef>sd_bus **<parameter>bus</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_default_user</function></funcdef>
        <paramdef>sd_bus **<parameter>bus</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_default_system</function></funcdef>
        <paramdef>sd_bus **<parameter>bus</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_open</function></funcdef>
        <paramdef>sd_bus **<parameter>bus</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_open_user</function></funcdef>
        <paramdef>sd_bus **<parameter>bus</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_open_system</function></funcdef>
        <paramdef>sd_bus **<parameter>bus</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_open_system_remote</function></funcdef>
        <paramdef>sd_bus **<parameter>bus</parameter></paramdef>
        <paramdef>const char *<parameter>host</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_open_system_machine</function></funcdef>
        <paramdef>sd_bus **<parameter>bus</parameter></paramdef>
        <paramdef>const char *<parameter>machine</parameter></paramdef>
      </funcprototype>

    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para><function>sd_bus_default()</function> acquires a bus
    connection object to the user bus when invoked in user context or
    to the system bus otherwise. The connection object is associated
    to the calling thread. Each time the function is invoked from the
    same thread the same object is returned, but its reference count
    increased by one, as long as at least one reference is kept. When
    the last reference to the connection is dropped (using the
    <function>sd_bus_unref()</function> call), the connection is
    terminated. Note that the connection is not automatically
    terminated when the associated thread ends. It is important to
    drop the last reference to the bus connection explicitly before
    the thread ends or otherwise the connection will be leaked.</para>

    <para><function>sd_bus_default_user()</function> returns a user
    bus connection object associated to the calling thread.
    <function>sd_bus_default_system()</function> is similar, but
    connects to the system bus.</para>

    <para><function>sd_bus_open()</function> creates a new,
    independent bus connection to the user bus when invoked in user
    context or the system bus
    otherwise. <function>sd_bus_open_user()</function> is similar, but
    connects only to the user bus.
    <function>sd_bus_open_system()</function> does the same, but
    connects to the system bus. In contrast to
    <function>sd_bus_default()</function>,
    <function>sd_bus_default_user()</function>,
    <function>sd_bus_default_system()</function> these calls return
    new, independent connection objects that are not associated with
    the invoking thread and are not shared between multiple
    invocations. It is recommended to share connections per thread to
    efficiently make use the available resources. Thus, it is
    recommended to use <function>sd_bus_default()</function>,
    <function>sd_bus_default_user()</function>,
    <function>sd_bus_default_system()</function> to connect to the
    user or system buses.</para>

    <para>If the <varname>$DBUS_SESSION_BUS_ADDRESS</varname> environment
    variable is set
    (cf. <citerefentry project='man-pages'><refentrytitle>environ</refentrytitle><manvolnum>7</manvolnum></citerefentry>),
    it will be used as the address of the user bus. This variable can
    contain multiple addresses separated by <literal>;</literal>. If
    this variable is not set, a suitable default for the default user
    D-Bus instance will be used.</para>

    <para>If the <varname>$DBUS_SYSTEM_BUS_ADDRESS</varname>
    environment variable is set, it will be used as the address of the
    system bus. This variable uses the same syntax as
    <varname>$DBUS_SESSION_BUS_ADDRESS</varname>. If this variable is
    not set, a suitable default for the default system D-Bus instance
    will be used.</para>

    <para><function>sd_bus_open_system_remote()</function> connects to
    the system bus on the specified <parameter>host</parameter> using
    SSH. <parameter>host</parameter> consists of an optional user name
    followed by the <literal>@</literal> symbol, and the hostname.
    </para>

    <para><function>sd_bus_open_system_container()</function> connects
    to the system bus in the specified <parameter>machine</parameter>,
    where <parameter>machine</parameter> is the name of a local
    container.  See
    <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
    for more information about "machines".</para>

  </refsect1>

  <refsect1>
    <title>Return Value</title>

    <para>On success, these calls return 0 or a positive
    integer. On failure, these calls return a negative
    errno-style error code.</para>
  </refsect1>

  <refsect1>
    <title>Reference ownership</title>
    <para>The functions <function>sd_bus_open_user()</function>,
    <function>sd_bus_open()</function>,
    <function>sd_bus_open_system()</function>,
    <function>sd_bus_open_system_remote()</function>, and
    <function>sd_bus_open_system_machine()</function> return a new
    object and the caller owns the sole reference. When not needed
    anymore, this reference should be destroyed with
    <citerefentry><refentrytitle>sd_bus_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
    </para>

    <para>The functions <function>sd_bus_default()</function>,
    <function>sd_bus_default_user()</function> and
    <function>sd_bus_default_system()</function> do not necessarily
    create a new object, but increase the connection reference by
    one. Use
    <citerefentry><refentrytitle>sd_bus_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    to drop the reference.</para>
  </refsect1>

  <refsect1>
    <title>Errors</title>

    <para>Returned errors may indicate the following problems:</para>

    <variablelist>

      <varlistentry>
        <term><constant>-EINVAL</constant></term>

        <listitem><para>The specified parameters are invalid.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><constant>-ENOMEM</constant></term>

        <listitem><para>Memory allocation failed.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><constant>-ESOCKTNOSUPPORT</constant></term>

        <listitem><para>The protocol version required to connect to the selected bus is not supported.</para></listitem>
      </varlistentry>
    </variablelist>

    <para>In addition, any further connection-related errors may be
    by returned. See <citerefentry><refentrytitle>sd_bus_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
  </refsect1>

  <refsect1>
    <title>Notes</title>

    <para><function>sd_bus_open_user()</function> and the other
    functions described here are available as a shared library, which
    can be compiled and linked to with the
    <constant>libsystemd</constant> <citerefentry
    project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
    file.</para>
  </refsect1>

  <refsect1>
    <title>See Also</title>

    <para>
      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_bus_ref</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_bus_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry project='die-net'><refentrytitle>ssh</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd-machined.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
    </para>
  </refsect1>

</refentry>