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514094f9 | 1 | <?xml version='1.0'?> |
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2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" |
3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> | |
db9ecf05 | 4 | <!-- SPDX-License-Identifier: LGPL-2.1-or-later --> |
cd6d5e1c | 5 | |
7d6b2723 | 6 | <refentry id="sd_bus_default" xmlns:xi="http://www.w3.org/2001/XInclude"> |
cd6d5e1c ZJS |
7 | |
8 | <refentryinfo> | |
4a2af8d7 | 9 | <title>sd_bus_default</title> |
cd6d5e1c | 10 | <productname>systemd</productname> |
cd6d5e1c ZJS |
11 | </refentryinfo> |
12 | ||
13 | <refmeta> | |
4a2af8d7 | 14 | <refentrytitle>sd_bus_default</refentrytitle> |
cd6d5e1c ZJS |
15 | <manvolnum>3</manvolnum> |
16 | </refmeta> | |
17 | ||
18 | <refnamediv> | |
4a2af8d7 LP |
19 | <refname>sd_bus_default</refname> |
20 | <refname>sd_bus_default_user</refname> | |
21 | <refname>sd_bus_default_system</refname> | |
22 | ||
23 | <refname>sd_bus_open</refname> | |
f00ded93 | 24 | <refname>sd_bus_open_with_description</refname> |
cd6d5e1c | 25 | <refname>sd_bus_open_user</refname> |
f00ded93 | 26 | <refname>sd_bus_open_user_with_description</refname> |
ba4a31b7 | 27 | <refname>sd_bus_open_user_machine</refname> |
cd6d5e1c | 28 | <refname>sd_bus_open_system</refname> |
f00ded93 | 29 | <refname>sd_bus_open_system_with_description</refname> |
cd6d5e1c | 30 | <refname>sd_bus_open_system_remote</refname> |
4a2af8d7 | 31 | <refname>sd_bus_open_system_machine</refname> |
cd6d5e1c | 32 | |
4a2af8d7 | 33 | <refpurpose>Acquire a connection to a system or user bus</refpurpose> |
cd6d5e1c ZJS |
34 | </refnamediv> |
35 | ||
36 | <refsynopsisdiv> | |
37 | <funcsynopsis> | |
38 | <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> | |
39 | ||
40 | <funcprototype> | |
4a2af8d7 | 41 | <funcdef>int <function>sd_bus_default</function></funcdef> |
8dc385e7 | 42 | <paramdef>sd_bus **<parameter>bus</parameter></paramdef> |
cd6d5e1c ZJS |
43 | </funcprototype> |
44 | ||
45 | <funcprototype> | |
4a2af8d7 | 46 | <funcdef>int <function>sd_bus_default_user</function></funcdef> |
8dc385e7 | 47 | <paramdef>sd_bus **<parameter>bus</parameter></paramdef> |
cd6d5e1c ZJS |
48 | </funcprototype> |
49 | ||
50 | <funcprototype> | |
4a2af8d7 | 51 | <funcdef>int <function>sd_bus_default_system</function></funcdef> |
8dc385e7 | 52 | <paramdef>sd_bus **<parameter>bus</parameter></paramdef> |
cd6d5e1c ZJS |
53 | </funcprototype> |
54 | ||
55 | <funcprototype> | |
4a2af8d7 | 56 | <funcdef>int <function>sd_bus_open</function></funcdef> |
8dc385e7 | 57 | <paramdef>sd_bus **<parameter>bus</parameter></paramdef> |
cd6d5e1c ZJS |
58 | </funcprototype> |
59 | ||
f00ded93 ZJS |
60 | <funcprototype> |
61 | <funcdef>int <function>sd_bus_open_with_description</function></funcdef> | |
62 | <paramdef>sd_bus **<parameter>bus</parameter></paramdef> | |
63 | <paramdef>const char *<parameter>description</parameter></paramdef> | |
64 | </funcprototype> | |
65 | ||
cd6d5e1c | 66 | <funcprototype> |
4a2af8d7 | 67 | <funcdef>int <function>sd_bus_open_user</function></funcdef> |
8dc385e7 | 68 | <paramdef>sd_bus **<parameter>bus</parameter></paramdef> |
cd6d5e1c ZJS |
69 | </funcprototype> |
70 | ||
f00ded93 ZJS |
71 | <funcprototype> |
72 | <funcdef>int <function>sd_bus_open_user_with_description</function></funcdef> | |
73 | <paramdef>sd_bus **<parameter>bus</parameter></paramdef> | |
74 | <paramdef>const char *<parameter>description</parameter></paramdef> | |
75 | </funcprototype> | |
76 | ||
ba4a31b7 LP |
77 | <funcprototype> |
78 | <funcdef>int <function>sd_bus_open_user_machine</function></funcdef> | |
79 | <paramdef>sd_bus **<parameter>bus</parameter></paramdef> | |
80 | <paramdef>const char *<parameter>machine</parameter></paramdef> | |
81 | </funcprototype> | |
82 | ||
cd6d5e1c | 83 | <funcprototype> |
4a2af8d7 | 84 | <funcdef>int <function>sd_bus_open_system</function></funcdef> |
8dc385e7 | 85 | <paramdef>sd_bus **<parameter>bus</parameter></paramdef> |
cd6d5e1c | 86 | </funcprototype> |
4a2af8d7 | 87 | |
f00ded93 ZJS |
88 | <funcprototype> |
89 | <funcdef>int <function>sd_bus_open_system_with_description</function></funcdef> | |
90 | <paramdef>sd_bus **<parameter>bus</parameter></paramdef> | |
91 | <paramdef>const char *<parameter>description</parameter></paramdef> | |
92 | </funcprototype> | |
93 | ||
4a2af8d7 LP |
94 | <funcprototype> |
95 | <funcdef>int <function>sd_bus_open_system_remote</function></funcdef> | |
96 | <paramdef>sd_bus **<parameter>bus</parameter></paramdef> | |
97 | <paramdef>const char *<parameter>host</parameter></paramdef> | |
98 | </funcprototype> | |
99 | ||
100 | <funcprototype> | |
101 | <funcdef>int <function>sd_bus_open_system_machine</function></funcdef> | |
102 | <paramdef>sd_bus **<parameter>bus</parameter></paramdef> | |
103 | <paramdef>const char *<parameter>machine</parameter></paramdef> | |
104 | </funcprototype> | |
105 | ||
cd6d5e1c ZJS |
106 | </funcsynopsis> |
107 | </refsynopsisdiv> | |
108 | ||
109 | <refsect1> | |
110 | <title>Description</title> | |
111 | ||
4a2af8d7 | 112 | <para><function>sd_bus_default()</function> acquires a bus |
f0f7cbd4 LB |
113 | connection object to the user bus when invoked from within a user |
114 | slice (any session under <literal>user-*.slice</literal>, e.g.: | |
115 | <literal>user@1000.service</literal>), or to the system bus | |
116 | otherwise. The connection object is associated with the calling | |
117 | thread. Each time the function is invoked from the same thread, | |
118 | the same object is returned, but its reference count is increased | |
119 | by one, as long as at least one reference is kept. When the last | |
120 | reference to the connection is dropped (using the | |
850df10a LP |
121 | <citerefentry><refentrytitle>sd_bus_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
122 | call), the connection is terminated. Note that the connection is | |
123 | not automatically terminated when the associated thread ends. It | |
124 | is important to drop the last reference to the bus connection | |
a8eaaee7 JE |
125 | explicitly before the thread ends, as otherwise, the connection will |
126 | leak. Also, queued but unread or unwritten messages keep the | |
b898f9bd | 127 | bus referenced, see below.</para> |
4a2af8d7 LP |
128 | |
129 | <para><function>sd_bus_default_user()</function> returns a user | |
b898f9bd | 130 | bus connection object associated with the calling thread. |
4a2af8d7 | 131 | <function>sd_bus_default_system()</function> is similar, but |
850df10a LP |
132 | connects to the system bus. Note that |
133 | <function>sd_bus_default()</function> is identical to these two | |
134 | calls, depending on the execution context.</para> | |
cd6d5e1c | 135 | |
4a2af8d7 LP |
136 | <para><function>sd_bus_open()</function> creates a new, |
137 | independent bus connection to the user bus when invoked in user | |
850df10a | 138 | context, or the system bus |
4a2af8d7 LP |
139 | otherwise. <function>sd_bus_open_user()</function> is similar, but |
140 | connects only to the user bus. | |
141 | <function>sd_bus_open_system()</function> does the same, but | |
142 | connects to the system bus. In contrast to | |
143 | <function>sd_bus_default()</function>, | |
a8eaaee7 | 144 | <function>sd_bus_default_user()</function>, and |
b938cb90 | 145 | <function>sd_bus_default_system()</function>, these calls return |
4a2af8d7 LP |
146 | new, independent connection objects that are not associated with |
147 | the invoking thread and are not shared between multiple | |
148 | invocations. It is recommended to share connections per thread to | |
149 | efficiently make use the available resources. Thus, it is | |
150 | recommended to use <function>sd_bus_default()</function>, | |
a8eaaee7 | 151 | <function>sd_bus_default_user()</function> and |
4a2af8d7 | 152 | <function>sd_bus_default_system()</function> to connect to the |
ff9b60f3 | 153 | user or system buses.</para> |
4a2af8d7 | 154 | |
f00ded93 ZJS |
155 | <para><function>sd_bus_open_with_description()</function>, |
156 | <function>sd_bus_open_user_with_description()</function>, and | |
157 | <function>sd_bus_open_system_with_description()</function> are similar to | |
158 | <function>sd_bus_open()</function>, <function>sd_bus_open_user()</function>, and | |
159 | <function>sd_bus_open_system()</function>, but allow a description string to be set, see | |
160 | <citerefentry><refentrytitle>sd_bus_set_description</refentrytitle><manvolnum>3</manvolnum></citerefentry>. | |
161 | <parameter>description</parameter> may be <constant>NULL</constant>, in which case this function | |
162 | is equivalent to <function>sd_bus_open()</function>. This description string is used in log | |
163 | messages about the bus object, and including a "name" for the bus makes them easier to | |
164 | understand. Some messages are emitted during bus initialization, hence using this function is | |
5e2b0e1c | 165 | preferable to setting the description later with |
f00ded93 ZJS |
166 | <function>sd_bus_open_with_description()</function>. The argument is copied internally and will |
167 | not be referenced after the function returns.</para> | |
168 | ||
66f756d4 | 169 | <para>If the <varname>$DBUS_SESSION_BUS_ADDRESS</varname> environment |
cd6d5e1c | 170 | variable is set |
5aded369 | 171 | (cf. <citerefentry project='man-pages'><refentrytitle>environ</refentrytitle><manvolnum>7</manvolnum></citerefentry>), |
cd6d5e1c ZJS |
172 | it will be used as the address of the user bus. This variable can |
173 | contain multiple addresses separated by <literal>;</literal>. If | |
174 | this variable is not set, a suitable default for the default user | |
175 | D-Bus instance will be used.</para> | |
176 | ||
4a2af8d7 LP |
177 | <para>If the <varname>$DBUS_SYSTEM_BUS_ADDRESS</varname> |
178 | environment variable is set, it will be used as the address of the | |
179 | system bus. This variable uses the same syntax as | |
180 | <varname>$DBUS_SESSION_BUS_ADDRESS</varname>. If this variable is | |
cd6d5e1c ZJS |
181 | not set, a suitable default for the default system D-Bus instance |
182 | will be used.</para> | |
183 | ||
f8f1e666 ZJS |
184 | <para><function>sd_bus_open_system_remote()</function> connects to the system bus on |
185 | the specified host using | |
082ac7bb | 186 | <citerefentry project='man-pages'><refentrytitle>ssh</refentrytitle><manvolnum>1</manvolnum></citerefentry>. |
f8f1e666 ZJS |
187 | <parameter>host</parameter> consists of an optional user name followed by the |
188 | <literal>@</literal> symbol, and the hostname, optionally followed by a | |
2e6fe090 SL |
189 | <literal>:</literal> and a port, optionally followed by a |
190 | <literal>/</literal> and a machine name. If the machine name is given, a connection | |
f8f1e666 ZJS |
191 | is created to the system bus in the specified container on the remote machine, and |
192 | otherwise a connection to the system bus on the specified host is created.</para> | |
193 | ||
194 | <para>Note that entering a container is a privileged operation, and will likely only | |
195 | work for the root user on the remote machine.</para> | |
cd6d5e1c | 196 | |
3f549982 | 197 | <para><function>sd_bus_open_system_machine()</function> connects to the system bus in the specified |
ba4a31b7 LP |
198 | <parameter>machine</parameter>, where <parameter>machine</parameter> is the name of a local container, |
199 | possibly prefixed by a user name and a separating <literal>@</literal>. If the container name is | |
200 | specified as the special string <literal>.host</literal> the connection is made to the local system. This | |
201 | is useful to connect to the local system bus as specific user, e.g. <literal>foobar@.host</literal> to | |
202 | connect to the local system bus as local user <literal>foobar</literal>. If the <literal>@</literal> | |
24ee0f9d | 203 | syntax is used either the left-hand side or the right-hand side may be omitted (but not both) in which |
ba4a31b7 LP |
204 | case the local user name or <literal>.host</literal> is implied. If the <literal>@</literal> syntax is |
205 | not used the connection is always made as root user. See | |
3f549982 ZJS |
206 | <citerefentry><refentrytitle>sd_bus_set_address</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
207 | for a description of the address syntax, and | |
208 | <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry> for more | |
209 | information about the "machine" concept. Note that connections into local containers are only available | |
210 | to privileged processes at this time.</para> | |
850df10a | 211 | |
ba4a31b7 LP |
212 | <para><function>sd_bus_open_user_machine()</function> is similar to |
213 | <function>sd_bus_open_system_machine()</function>, but connects to the user bus of the root user, or if | |
214 | the <literal>@</literal> syntax is used, of the specified user.</para> | |
215 | ||
850df10a | 216 | <para>These calls allocate a bus connection object and initiate |
67ad70e4 | 217 | the connection to a well-known bus of some form. An alternative to |
850df10a LP |
218 | using these high-level calls is to create an unconnected bus |
219 | object with | |
220 | <citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
221 | and to connect it with | |
222 | <citerefentry><refentrytitle>sd_bus_start</refentrytitle><manvolnum>3</manvolnum></citerefentry>. | |
223 | </para> | |
cd6d5e1c | 224 | |
cd6d5e1c ZJS |
225 | </refsect1> |
226 | ||
cd6d5e1c ZJS |
227 | <refsect1> |
228 | <title>Reference ownership</title> | |
850df10a LP |
229 | <para>The functions <function>sd_bus_open()</function>, |
230 | <function>sd_bus_open_user()</function>, | |
ba4a31b7 | 231 | <function>sd_bus_open_user_machine()</function>, |
cd6d5e1c ZJS |
232 | <function>sd_bus_open_system()</function>, |
233 | <function>sd_bus_open_system_remote()</function>, and | |
234 | <function>sd_bus_open_system_machine()</function> return a new | |
b898f9bd LP |
235 | connection object and the caller owns the sole reference. When not |
236 | needed anymore, this reference should be destroyed with | |
cd6d5e1c ZJS |
237 | <citerefentry><refentrytitle>sd_bus_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>. |
238 | </para> | |
239 | ||
4a2af8d7 LP |
240 | <para>The functions <function>sd_bus_default()</function>, |
241 | <function>sd_bus_default_user()</function> and | |
242 | <function>sd_bus_default_system()</function> do not necessarily | |
b898f9bd LP |
243 | create a new object, but increase the connection reference of an |
244 | existing connection object by one. Use | |
4a2af8d7 LP |
245 | <citerefentry><refentrytitle>sd_bus_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
246 | to drop the reference.</para> | |
db03761e | 247 | |
1004b2c7 LP |
248 | <para>Queued but unwritten/unread messages keep a reference to their bus connection object. For this reason, even |
249 | if an application dropped all references to a bus connection, it might not get destroyed right away. Until all | |
250 | incoming queued messages are read, and until all outgoing unwritten messages are written, the bus object will stay | |
251 | alive. <function>sd_bus_flush()</function> may be used to write all outgoing queued messages so they drop their | |
252 | references. To flush the unread incoming messages, use <function>sd_bus_close()</function>, which will also close | |
253 | the bus connection. When using the default bus logic, it is a good idea to first invoke | |
254 | <function>sd_bus_flush()</function> followed by <function>sd_bus_close()</function> when a thread or process | |
255 | terminates, and thus its bus connection object should be freed.</para> | |
256 | ||
257 | <para>Normally, slot objects (as created by | |
258 | <citerefentry><refentrytitle>sd_bus_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry> and similar | |
259 | calls) keep a reference to their bus connection object, too. Thus, as long as a bus slot object remains referenced | |
260 | its bus object will remain allocated too. Optionally, bus slot objects may be placed in "floating" mode. When in | |
261 | floating mode the life cycle of the bus slot object is bound to the bus object, i.e. when the bus object is freed | |
262 | the bus slot object is automatically unreferenced too. The floating state of a slot object may be controlled | |
263 | explicitly with | |
264 | <citerefentry><refentrytitle>sd_bus_slot_set_floating</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
265 | though usually floating bus slot objects are created by passing <constant>NULL</constant> as the | |
266 | <parameter>slot</parameter> parameter of <function>sd_bus_add_match()</function> and related calls, thus indicating | |
267 | that the caller is not directly interested in referencing and managing the bus slot object.</para> | |
b898f9bd | 268 | |
b938cb90 | 269 | <para>The life cycle of the default bus connection should be the |
b898f9bd LP |
270 | responsibility of the code that creates/owns the thread the |
271 | default bus connection object is associated with. Library code | |
272 | should neither call <function>sd_bus_flush()</function> nor | |
273 | <function>sd_bus_close()</function> on default bus objects unless | |
274 | it does so in its own private, self-allocated thread. Library code | |
275 | should not use the default bus object in other threads unless it | |
b938cb90 | 276 | is clear that the program using it will life cycle the bus |
b898f9bd LP |
277 | connection object and flush and close it before exiting from the |
278 | thread. In libraries where it is not clear that the calling | |
b938cb90 | 279 | program will life cycle the bus connection object, it is hence |
b898f9bd LP |
280 | recommended to use <function>sd_bus_open_system()</function> |
281 | instead of <function>sd_bus_default_system()</function> and | |
282 | related calls.</para> | |
283 | </refsect1> | |
284 | ||
285 | <refsect1> | |
286 | <title>Return Value</title> | |
287 | ||
288 | <para>On success, these calls return 0 or a positive | |
289 | integer. On failure, these calls return a negative | |
290 | errno-style error code.</para> | |
cd6d5e1c | 291 | |
b1de39de ZJS |
292 | <refsect2> |
293 | <title>Errors</title> | |
cd6d5e1c | 294 | |
b1de39de | 295 | <para>Returned errors may indicate the following problems:</para> |
cd6d5e1c | 296 | |
b1de39de | 297 | <variablelist> |
b1de39de ZJS |
298 | <varlistentry> |
299 | <term><constant>-EINVAL</constant></term> | |
cd6d5e1c | 300 | |
b1de39de ZJS |
301 | <listitem><para>The specified parameters are invalid.</para></listitem> |
302 | </varlistentry> | |
cd6d5e1c | 303 | |
ab4a88eb ZJS |
304 | <varlistentry> |
305 | <term><constant>-ENOMEDIUM</constant></term> | |
306 | ||
307 | <listitem><para>The requested bus type is not available because of invalid environment (for example | |
308 | the user session bus is not available because <varname>$XDG_RUNTIME_DIR</varname> is not set). | |
ec07c3c8 AK |
309 | </para> |
310 | ||
311 | <xi:include href="version-info.xml" xpointer="v247"/></listitem> | |
ab4a88eb ZJS |
312 | </varlistentry> |
313 | ||
b1de39de ZJS |
314 | <varlistentry> |
315 | <term><constant>-ENOMEM</constant></term> | |
cd6d5e1c | 316 | |
b1de39de ZJS |
317 | <listitem><para>Memory allocation failed.</para></listitem> |
318 | </varlistentry> | |
cd6d5e1c | 319 | |
b1de39de ZJS |
320 | <varlistentry> |
321 | <term><constant>-ESOCKTNOSUPPORT</constant></term> | |
4a2af8d7 | 322 | |
b1de39de ZJS |
323 | <listitem><para>The protocol version required to connect to the selected bus is not |
324 | supported.</para></listitem> | |
325 | </varlistentry> | |
326 | </variablelist> | |
4a2af8d7 | 327 | |
27622235 | 328 | <para>In addition, other connection-related errors may be returned. See |
b1de39de ZJS |
329 | <citerefentry><refentrytitle>sd_bus_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> |
330 | </refsect2> | |
cd6d5e1c ZJS |
331 | </refsect1> |
332 | ||
7d6b2723 | 333 | <xi:include href="libsystemd-pkgconfig.xml" /> |
cd6d5e1c ZJS |
334 | |
335 | <refsect1> | |
69106f47 | 336 | <title>History</title> |
00f95506 AK |
337 | <para><function>sd_bus_default()</function>, |
338 | <function>sd_bus_default_user()</function>, | |
339 | <function>sd_bus_default_system()</function>, | |
340 | <function>sd_bus_open()</function>, | |
341 | <function>sd_bus_open_user()</function>, | |
342 | <function>sd_bus_open_system()</function>, | |
343 | <function>sd_bus_open_system_remote()</function>, and | |
344 | <function>sd_bus_open_system_machine()</function> were added in version 220.</para> | |
345 | <para><function>sd_bus_open_with_description()</function>, | |
346 | <function>sd_bus_open_user_with_description()</function>, and | |
347 | <function>sd_bus_open_system_with_description()</function> were added in version 240.</para> | |
69106f47 AK |
348 | <para><function>sd_bus_open_user_machine()</function> was added in version 248.</para> |
349 | </refsect1> | |
350 | ||
351 | <refsect1> | |
cd6d5e1c ZJS |
352 | <title>See Also</title> |
353 | ||
13a69c12 DT |
354 | <para><simplelist type="inline"> |
355 | <member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member> | |
356 | <member><citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry></member> | |
357 | <member><citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry></member> | |
358 | <member><citerefentry><refentrytitle>sd_bus_ref</refentrytitle><manvolnum>3</manvolnum></citerefentry></member> | |
359 | <member><citerefentry><refentrytitle>sd_bus_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry></member> | |
360 | <member><citerefentry><refentrytitle>sd_bus_close</refentrytitle><manvolnum>3</manvolnum></citerefentry></member> | |
361 | <member><citerefentry project='man-pages'><refentrytitle>ssh</refentrytitle><manvolnum>1</manvolnum></citerefentry></member> | |
362 | <member><citerefentry><refentrytitle>systemd-machined.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member> | |
363 | <member><citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry></member> | |
364 | </simplelist></para> | |
cd6d5e1c ZJS |
365 | </refsect1> |
366 | ||
367 | </refentry> |