]>
Commit | Line | Data |
---|---|---|
514094f9 | 1 | <?xml version='1.0'?> |
cd6d5e1c | 2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" |
12b42c76 | 3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
cd6d5e1c ZJS |
4 | |
5 | <!-- | |
572eb058 | 6 | SPDX-License-Identifier: LGPL-2.1+ |
cd6d5e1c ZJS |
7 | --> |
8 | ||
7d6b2723 | 9 | <refentry id="sd_bus_default" xmlns:xi="http://www.w3.org/2001/XInclude"> |
cd6d5e1c ZJS |
10 | |
11 | <refentryinfo> | |
4a2af8d7 | 12 | <title>sd_bus_default</title> |
cd6d5e1c | 13 | <productname>systemd</productname> |
cd6d5e1c ZJS |
14 | </refentryinfo> |
15 | ||
16 | <refmeta> | |
4a2af8d7 | 17 | <refentrytitle>sd_bus_default</refentrytitle> |
cd6d5e1c ZJS |
18 | <manvolnum>3</manvolnum> |
19 | </refmeta> | |
20 | ||
21 | <refnamediv> | |
4a2af8d7 LP |
22 | <refname>sd_bus_default</refname> |
23 | <refname>sd_bus_default_user</refname> | |
24 | <refname>sd_bus_default_system</refname> | |
25 | ||
26 | <refname>sd_bus_open</refname> | |
cd6d5e1c ZJS |
27 | <refname>sd_bus_open_user</refname> |
28 | <refname>sd_bus_open_system</refname> | |
29 | <refname>sd_bus_open_system_remote</refname> | |
4a2af8d7 | 30 | <refname>sd_bus_open_system_machine</refname> |
cd6d5e1c | 31 | |
4a2af8d7 | 32 | <refpurpose>Acquire a connection to a system or user bus</refpurpose> |
cd6d5e1c ZJS |
33 | </refnamediv> |
34 | ||
35 | <refsynopsisdiv> | |
36 | <funcsynopsis> | |
37 | <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> | |
38 | ||
39 | <funcprototype> | |
4a2af8d7 | 40 | <funcdef>int <function>sd_bus_default</function></funcdef> |
8dc385e7 | 41 | <paramdef>sd_bus **<parameter>bus</parameter></paramdef> |
cd6d5e1c ZJS |
42 | </funcprototype> |
43 | ||
44 | <funcprototype> | |
4a2af8d7 | 45 | <funcdef>int <function>sd_bus_default_user</function></funcdef> |
8dc385e7 | 46 | <paramdef>sd_bus **<parameter>bus</parameter></paramdef> |
cd6d5e1c ZJS |
47 | </funcprototype> |
48 | ||
49 | <funcprototype> | |
4a2af8d7 | 50 | <funcdef>int <function>sd_bus_default_system</function></funcdef> |
8dc385e7 | 51 | <paramdef>sd_bus **<parameter>bus</parameter></paramdef> |
cd6d5e1c ZJS |
52 | </funcprototype> |
53 | ||
54 | <funcprototype> | |
4a2af8d7 | 55 | <funcdef>int <function>sd_bus_open</function></funcdef> |
8dc385e7 | 56 | <paramdef>sd_bus **<parameter>bus</parameter></paramdef> |
cd6d5e1c ZJS |
57 | </funcprototype> |
58 | ||
59 | <funcprototype> | |
4a2af8d7 | 60 | <funcdef>int <function>sd_bus_open_user</function></funcdef> |
8dc385e7 | 61 | <paramdef>sd_bus **<parameter>bus</parameter></paramdef> |
cd6d5e1c ZJS |
62 | </funcprototype> |
63 | ||
64 | <funcprototype> | |
4a2af8d7 | 65 | <funcdef>int <function>sd_bus_open_system</function></funcdef> |
8dc385e7 | 66 | <paramdef>sd_bus **<parameter>bus</parameter></paramdef> |
cd6d5e1c | 67 | </funcprototype> |
4a2af8d7 LP |
68 | |
69 | <funcprototype> | |
70 | <funcdef>int <function>sd_bus_open_system_remote</function></funcdef> | |
71 | <paramdef>sd_bus **<parameter>bus</parameter></paramdef> | |
72 | <paramdef>const char *<parameter>host</parameter></paramdef> | |
73 | </funcprototype> | |
74 | ||
75 | <funcprototype> | |
76 | <funcdef>int <function>sd_bus_open_system_machine</function></funcdef> | |
77 | <paramdef>sd_bus **<parameter>bus</parameter></paramdef> | |
78 | <paramdef>const char *<parameter>machine</parameter></paramdef> | |
79 | </funcprototype> | |
80 | ||
cd6d5e1c ZJS |
81 | </funcsynopsis> |
82 | </refsynopsisdiv> | |
83 | ||
84 | <refsect1> | |
85 | <title>Description</title> | |
86 | ||
4a2af8d7 | 87 | <para><function>sd_bus_default()</function> acquires a bus |
850df10a | 88 | connection object to the user bus when invoked in user context, or |
4a2af8d7 | 89 | to the system bus otherwise. The connection object is associated |
b898f9bd | 90 | with the calling thread. Each time the function is invoked from |
b938cb90 | 91 | the same thread, the same object is returned, but its reference |
b898f9bd | 92 | count is increased by one, as long as at least one reference is |
850df10a LP |
93 | kept. When the last reference to the connection is dropped (using |
94 | the | |
95 | <citerefentry><refentrytitle>sd_bus_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
96 | call), the connection is terminated. Note that the connection is | |
97 | not automatically terminated when the associated thread ends. It | |
98 | is important to drop the last reference to the bus connection | |
a8eaaee7 JE |
99 | explicitly before the thread ends, as otherwise, the connection will |
100 | leak. Also, queued but unread or unwritten messages keep the | |
b898f9bd | 101 | bus referenced, see below.</para> |
4a2af8d7 LP |
102 | |
103 | <para><function>sd_bus_default_user()</function> returns a user | |
b898f9bd | 104 | bus connection object associated with the calling thread. |
4a2af8d7 | 105 | <function>sd_bus_default_system()</function> is similar, but |
850df10a LP |
106 | connects to the system bus. Note that |
107 | <function>sd_bus_default()</function> is identical to these two | |
108 | calls, depending on the execution context.</para> | |
cd6d5e1c | 109 | |
4a2af8d7 LP |
110 | <para><function>sd_bus_open()</function> creates a new, |
111 | independent bus connection to the user bus when invoked in user | |
850df10a | 112 | context, or the system bus |
4a2af8d7 LP |
113 | otherwise. <function>sd_bus_open_user()</function> is similar, but |
114 | connects only to the user bus. | |
115 | <function>sd_bus_open_system()</function> does the same, but | |
116 | connects to the system bus. In contrast to | |
117 | <function>sd_bus_default()</function>, | |
a8eaaee7 | 118 | <function>sd_bus_default_user()</function>, and |
b938cb90 | 119 | <function>sd_bus_default_system()</function>, these calls return |
4a2af8d7 LP |
120 | new, independent connection objects that are not associated with |
121 | the invoking thread and are not shared between multiple | |
122 | invocations. It is recommended to share connections per thread to | |
123 | efficiently make use the available resources. Thus, it is | |
124 | recommended to use <function>sd_bus_default()</function>, | |
a8eaaee7 | 125 | <function>sd_bus_default_user()</function> and |
4a2af8d7 | 126 | <function>sd_bus_default_system()</function> to connect to the |
ff9b60f3 | 127 | user or system buses.</para> |
4a2af8d7 | 128 | |
66f756d4 | 129 | <para>If the <varname>$DBUS_SESSION_BUS_ADDRESS</varname> environment |
cd6d5e1c | 130 | variable is set |
5aded369 | 131 | (cf. <citerefentry project='man-pages'><refentrytitle>environ</refentrytitle><manvolnum>7</manvolnum></citerefentry>), |
cd6d5e1c ZJS |
132 | it will be used as the address of the user bus. This variable can |
133 | contain multiple addresses separated by <literal>;</literal>. If | |
134 | this variable is not set, a suitable default for the default user | |
135 | D-Bus instance will be used.</para> | |
136 | ||
4a2af8d7 LP |
137 | <para>If the <varname>$DBUS_SYSTEM_BUS_ADDRESS</varname> |
138 | environment variable is set, it will be used as the address of the | |
139 | system bus. This variable uses the same syntax as | |
140 | <varname>$DBUS_SESSION_BUS_ADDRESS</varname>. If this variable is | |
cd6d5e1c ZJS |
141 | not set, a suitable default for the default system D-Bus instance |
142 | will be used.</para> | |
143 | ||
f8f1e666 ZJS |
144 | <para><function>sd_bus_open_system_remote()</function> connects to the system bus on |
145 | the specified host using | |
146 | <citerefentry project='die-net'><refentrytitle>ssh</refentrytitle><manvolnum>1</manvolnum></citerefentry>. | |
147 | <parameter>host</parameter> consists of an optional user name followed by the | |
148 | <literal>@</literal> symbol, and the hostname, optionally followed by a | |
149 | <literal>:</literal> and a machine name. If the machine name is given, a connection | |
150 | is created to the system bus in the specified container on the remote machine, and | |
151 | otherwise a connection to the system bus on the specified host is created.</para> | |
152 | ||
153 | <para>Note that entering a container is a privileged operation, and will likely only | |
154 | work for the root user on the remote machine.</para> | |
cd6d5e1c | 155 | |
30cd7638 | 156 | <para><function>sd_bus_open_system_machine()</function> connects |
174299e3 | 157 | to the system bus in the specified <parameter>machine</parameter>, |
4a2af8d7 LP |
158 | where <parameter>machine</parameter> is the name of a local |
159 | container. See | |
cd6d5e1c | 160 | <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry> |
850df10a LP |
161 | for more information about the "machine" concept. Note that |
162 | connections into local containers are only available to privileged | |
163 | processes at this time.</para> | |
164 | ||
165 | <para>These calls allocate a bus connection object and initiate | |
67ad70e4 | 166 | the connection to a well-known bus of some form. An alternative to |
850df10a LP |
167 | using these high-level calls is to create an unconnected bus |
168 | object with | |
169 | <citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
170 | and to connect it with | |
171 | <citerefentry><refentrytitle>sd_bus_start</refentrytitle><manvolnum>3</manvolnum></citerefentry>. | |
172 | </para> | |
cd6d5e1c | 173 | |
cd6d5e1c ZJS |
174 | </refsect1> |
175 | ||
cd6d5e1c ZJS |
176 | <refsect1> |
177 | <title>Reference ownership</title> | |
850df10a LP |
178 | <para>The functions <function>sd_bus_open()</function>, |
179 | <function>sd_bus_open_user()</function>, | |
cd6d5e1c ZJS |
180 | <function>sd_bus_open_system()</function>, |
181 | <function>sd_bus_open_system_remote()</function>, and | |
182 | <function>sd_bus_open_system_machine()</function> return a new | |
b898f9bd LP |
183 | connection object and the caller owns the sole reference. When not |
184 | needed anymore, this reference should be destroyed with | |
cd6d5e1c ZJS |
185 | <citerefentry><refentrytitle>sd_bus_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>. |
186 | </para> | |
187 | ||
4a2af8d7 LP |
188 | <para>The functions <function>sd_bus_default()</function>, |
189 | <function>sd_bus_default_user()</function> and | |
190 | <function>sd_bus_default_system()</function> do not necessarily | |
b898f9bd LP |
191 | create a new object, but increase the connection reference of an |
192 | existing connection object by one. Use | |
4a2af8d7 LP |
193 | <citerefentry><refentrytitle>sd_bus_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
194 | to drop the reference.</para> | |
db03761e | 195 | |
1004b2c7 LP |
196 | <para>Queued but unwritten/unread messages keep a reference to their bus connection object. For this reason, even |
197 | if an application dropped all references to a bus connection, it might not get destroyed right away. Until all | |
198 | incoming queued messages are read, and until all outgoing unwritten messages are written, the bus object will stay | |
199 | alive. <function>sd_bus_flush()</function> may be used to write all outgoing queued messages so they drop their | |
200 | references. To flush the unread incoming messages, use <function>sd_bus_close()</function>, which will also close | |
201 | the bus connection. When using the default bus logic, it is a good idea to first invoke | |
202 | <function>sd_bus_flush()</function> followed by <function>sd_bus_close()</function> when a thread or process | |
203 | terminates, and thus its bus connection object should be freed.</para> | |
204 | ||
205 | <para>Normally, slot objects (as created by | |
206 | <citerefentry><refentrytitle>sd_bus_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry> and similar | |
207 | calls) keep a reference to their bus connection object, too. Thus, as long as a bus slot object remains referenced | |
208 | its bus object will remain allocated too. Optionally, bus slot objects may be placed in "floating" mode. When in | |
209 | floating mode the life cycle of the bus slot object is bound to the bus object, i.e. when the bus object is freed | |
210 | the bus slot object is automatically unreferenced too. The floating state of a slot object may be controlled | |
211 | explicitly with | |
212 | <citerefentry><refentrytitle>sd_bus_slot_set_floating</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
213 | though usually floating bus slot objects are created by passing <constant>NULL</constant> as the | |
214 | <parameter>slot</parameter> parameter of <function>sd_bus_add_match()</function> and related calls, thus indicating | |
215 | that the caller is not directly interested in referencing and managing the bus slot object.</para> | |
b898f9bd | 216 | |
b938cb90 | 217 | <para>The life cycle of the default bus connection should be the |
b898f9bd LP |
218 | responsibility of the code that creates/owns the thread the |
219 | default bus connection object is associated with. Library code | |
220 | should neither call <function>sd_bus_flush()</function> nor | |
221 | <function>sd_bus_close()</function> on default bus objects unless | |
222 | it does so in its own private, self-allocated thread. Library code | |
223 | should not use the default bus object in other threads unless it | |
b938cb90 | 224 | is clear that the program using it will life cycle the bus |
b898f9bd LP |
225 | connection object and flush and close it before exiting from the |
226 | thread. In libraries where it is not clear that the calling | |
b938cb90 | 227 | program will life cycle the bus connection object, it is hence |
b898f9bd LP |
228 | recommended to use <function>sd_bus_open_system()</function> |
229 | instead of <function>sd_bus_default_system()</function> and | |
230 | related calls.</para> | |
231 | </refsect1> | |
232 | ||
233 | <refsect1> | |
234 | <title>Return Value</title> | |
235 | ||
236 | <para>On success, these calls return 0 or a positive | |
237 | integer. On failure, these calls return a negative | |
238 | errno-style error code.</para> | |
cd6d5e1c ZJS |
239 | </refsect1> |
240 | ||
241 | <refsect1> | |
242 | <title>Errors</title> | |
243 | ||
244 | <para>Returned errors may indicate the following problems:</para> | |
245 | ||
246 | <variablelist> | |
247 | ||
248 | <varlistentry> | |
8474b70c | 249 | <term><constant>-EINVAL</constant></term> |
cd6d5e1c | 250 | |
4a2af8d7 | 251 | <listitem><para>The specified parameters are invalid.</para></listitem> |
cd6d5e1c ZJS |
252 | </varlistentry> |
253 | ||
254 | <varlistentry> | |
8474b70c | 255 | <term><constant>-ENOMEM</constant></term> |
cd6d5e1c ZJS |
256 | |
257 | <listitem><para>Memory allocation failed.</para></listitem> | |
258 | </varlistentry> | |
259 | ||
4a2af8d7 LP |
260 | <varlistentry> |
261 | <term><constant>-ESOCKTNOSUPPORT</constant></term> | |
262 | ||
263 | <listitem><para>The protocol version required to connect to the selected bus is not supported.</para></listitem> | |
264 | </varlistentry> | |
cd6d5e1c | 265 | </variablelist> |
4a2af8d7 LP |
266 | |
267 | <para>In addition, any further connection-related errors may be | |
268 | by returned. See <citerefentry><refentrytitle>sd_bus_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> | |
cd6d5e1c ZJS |
269 | </refsect1> |
270 | ||
7d6b2723 | 271 | <xi:include href="libsystemd-pkgconfig.xml" /> |
cd6d5e1c ZJS |
272 | |
273 | <refsect1> | |
274 | <title>See Also</title> | |
275 | ||
276 | <para> | |
277 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
278 | <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
279 | <citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
280 | <citerefentry><refentrytitle>sd_bus_ref</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
281 | <citerefentry><refentrytitle>sd_bus_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
3ba3a79d | 282 | <citerefentry project='die-net'><refentrytitle>ssh</refentrytitle><manvolnum>1</manvolnum></citerefentry>, |
cd6d5e1c ZJS |
283 | <citerefentry><refentrytitle>systemd-machined.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, |
284 | <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry> | |
285 | </para> | |
286 | </refsect1> | |
287 | ||
288 | </refentry> |