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1 | <?xml version='1.0'?> <!--*-nxml-*--> |
2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" | |
12b42c76 | 3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
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4 | |
5 | <!-- | |
572eb058 ZJS |
6 | SPDX-License-Identifier: LGPL-2.1+ |
7 | ||
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8 | This file is part of systemd. |
9 | ||
10 | Copyright 2013 Lennart Poettering | |
11 | ||
12 | systemd is free software; you can redistribute it and/or modify it | |
13 | under the terms of the GNU Lesser General Public License as published by | |
14 | the Free Software Foundation; either version 2.1 of the License, or | |
15 | (at your option) any later version. | |
16 | ||
17 | systemd is distributed in the hope that it will be useful, but | |
18 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
20 | Lesser General Public License for more details. | |
21 | ||
22 | You should have received a copy of the GNU Lesser General Public License | |
23 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
24 | --> | |
25 | ||
48f69d8f | 26 | <refentry id="sd_bus_request_name"> |
e7176abb | 27 | |
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28 | <refentryinfo> |
29 | <title>sd_bus_request_name</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_bus_request_name</refentrytitle> | |
44 | <manvolnum>3</manvolnum> | |
45 | </refmeta> | |
46 | ||
47 | <refnamediv> | |
48 | <refname>sd_bus_request_name</refname> | |
d97eac36 | 49 | <refname>sd_bus_request_name_async</refname> |
798d3a52 | 50 | <refname>sd_bus_release_name</refname> |
d97eac36 | 51 | <refname>sd_bus_release_name_async</refname> |
2a2e6a08 | 52 | <refpurpose>Request or release a well-known service name on a bus</refpurpose> |
798d3a52 ZJS |
53 | </refnamediv> |
54 | ||
55 | <refsynopsisdiv> | |
56 | <funcsynopsis> | |
57 | <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> | |
58 | ||
59 | <funcprototype> | |
60 | <funcdef>int <function>sd_bus_request_name</function></funcdef> | |
61 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> | |
62 | <paramdef>const char *<parameter>name</parameter></paramdef> | |
63 | <paramdef>uint64_t <parameter>flags</parameter></paramdef> | |
64 | </funcprototype> | |
65 | ||
d97eac36 LP |
66 | <funcprototype> |
67 | <funcdef>int <function>sd_bus_request_name_async</function></funcdef> | |
68 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> | |
69 | <paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef> | |
70 | <paramdef>const char *<parameter>name</parameter></paramdef> | |
71 | <paramdef>uint64_t <parameter>flags</parameter></paramdef> | |
72 | <paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef> | |
73 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
74 | </funcprototype> | |
75 | ||
798d3a52 ZJS |
76 | <funcprototype> |
77 | <funcdef>int <function>sd_bus_release_name</function></funcdef> | |
78 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> | |
79 | <paramdef>const char *<parameter>name</parameter></paramdef> | |
80 | </funcprototype> | |
d97eac36 LP |
81 | |
82 | <funcprototype> | |
83 | <funcdef>int <function>sd_bus_release_name_async</function></funcdef> | |
84 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> | |
85 | <paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef> | |
86 | <paramdef>const char *<parameter>name</parameter></paramdef> | |
87 | <paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef> | |
88 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
89 | </funcprototype> | |
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90 | </funcsynopsis> |
91 | </refsynopsisdiv> | |
92 | ||
93 | <refsect1> | |
94 | <title>Description</title> | |
95 | ||
d97eac36 LP |
96 | <para><function>sd_bus_request_name()</function> requests a well-known service name on a bus. It takes a bus |
97 | connection, a valid bus name and a flags parameter. The flags parameter is a combination of the following | |
98 | flags:</para> | |
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99 | |
100 | <variablelist> | |
101 | <varlistentry> | |
102 | <term><varname>SD_BUS_NAME_ALLOW_REPLACEMENT</varname></term> | |
103 | ||
d97eac36 LP |
104 | <listitem><para>After acquiring the name successfully, permit other peers to take over the name when they try |
105 | to acquire it with the <varname>SD_BUS_NAME_REPLACE_EXISTING</varname> flag set. If | |
106 | <varname>SD_BUS_NAME_ALLOW_REPLACEMENT</varname> is not set on the original request, such a request by other | |
107 | peers will be denied.</para></listitem> | |
798d3a52 ZJS |
108 | </varlistentry> |
109 | ||
110 | <varlistentry> | |
111 | <term><varname>SD_BUS_NAME_REPLACE_EXISTING</varname></term> | |
112 | ||
d97eac36 LP |
113 | <listitem><para>Take over the name if it is already acquired by another peer, and that other peer has permitted |
114 | takeover by setting <varname>SD_BUS_NAME_ALLOW_REPLACEMENT</varname> while acquiring it.</para></listitem> | |
798d3a52 ZJS |
115 | </varlistentry> |
116 | ||
117 | <varlistentry> | |
118 | <term><varname>SD_BUS_NAME_QUEUE</varname></term> | |
119 | ||
d97eac36 | 120 | <listitem><para>Queue the acquisition of the name when the name is already taken.</para></listitem> |
798d3a52 ZJS |
121 | </varlistentry> |
122 | </variablelist> | |
123 | ||
d97eac36 LP |
124 | <para><function>sd_bus_request_name()</function> operates in a synchronous fashion: a message requesting the name |
125 | is sent to the bus broker, and the call waits until the broker responds.</para> | |
126 | ||
127 | <para><function>sd_bus_request_name_async()</function> is an asynchronous version of of | |
128 | <function>sd_bus_release_name()</function>. Instead of waiting for the request to complete, the request message is | |
129 | enqueued. The specified <parameter>callback</parameter> will be called when the broker's response is received. If | |
130 | the parameter is specified as <constant>NULL</constant> a default implementation is used instead which will | |
131 | terminate the connection when the name cannot be acquired. The function returns a slot object in its | |
132 | <parameter>slot</parameter> parameter — if it is passed as non-<constant>NULL</constant> — which may be used as a | |
133 | reference to the name request operation. Use | |
134 | <citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> to destroy | |
135 | this reference. Note that destroying the reference will not unregister the name, but simply ensure the specified | |
136 | callback is no longer called.</para> | |
137 | ||
138 | <para><function>sd_bus_release_name()</function> releases an acquired well-known name. It takes a bus connection | |
139 | and a valid bus name as parameters. This function operates synchronously, sending a release request message to the | |
140 | bus broker and waiting for it to reply.</para> | |
141 | ||
142 | <para><function>sd_bus_release_name_async()</function> is an asynchronous version of | |
143 | <function>sd_bus_release_name()</function>. The specified <parameter>callback</parameter> function is called when | |
144 | the name has been released successfully. If specified as <constant>NULL</constant> a generic implementation is used | |
145 | that ignores the result of the operation. As above, the <parameter>slot</parameter> (if | |
146 | non-<constant>NULL</constant>) is set to an object that may be used to reference the operation.</para> | |
147 | ||
148 | <para>These functions are supported only on bus connections, i.e. connections to a bus broker and not on direct | |
149 | connections.</para> | |
798d3a52 ZJS |
150 | </refsect1> |
151 | ||
152 | <refsect1> | |
153 | <title>Return Value</title> | |
154 | ||
d97eac36 LP |
155 | <para>On success, these calls return 0 or a positive integer. On failure, these calls return a negative errno-style |
156 | error code.</para> | |
157 | ||
158 | <para>If <varname>SD_BUS_NAME_QUEUE</varname> is specified, <function>sd_bus_request_name()</function> will return | |
159 | 0 when the name is already taken by another peer and the client has been added to the queue for the name. In that | |
160 | case, the caller can subscribe to <literal>NameOwnerChanged</literal> signals to be notified when the name is | |
161 | successfully acquired. <function>sd_bus_request_name()</function> returns > 0 when the name has immediately | |
162 | been acquired successfully.</para> | |
798d3a52 ZJS |
163 | </refsect1> |
164 | ||
165 | <refsect1> | |
166 | <title>Errors</title> | |
167 | ||
168 | <para>Returned errors may indicate the following problems:</para> | |
169 | ||
170 | <variablelist> | |
171 | <varlistentry> | |
172 | <term><constant>-EALREADY</constant></term> | |
173 | ||
d97eac36 | 174 | <listitem><para>The caller already is the owner of the specified name.</para></listitem> |
798d3a52 ZJS |
175 | </varlistentry> |
176 | ||
177 | <varlistentry> | |
178 | <term><constant>-EEXIST</constant></term> | |
179 | ||
d97eac36 LP |
180 | <listitem><para>The name has already been acquired by a different peer, and SD_BUS_NAME_REPLACE_EXISTING was |
181 | not specified or the other peer did not specify SD_BUS_NAME_ALLOW_REPLACEMENT while acquiring the | |
798d3a52 ZJS |
182 | name.</para></listitem> |
183 | </varlistentry> | |
184 | ||
185 | <varlistentry> | |
186 | <term><constant>-ESRCH</constant></term> | |
187 | ||
d97eac36 LP |
188 | <listitem><para>It was attempted to release a name that is currently not registered on the |
189 | bus.</para></listitem> | |
798d3a52 ZJS |
190 | </varlistentry> |
191 | ||
192 | <varlistentry> | |
193 | <term><constant>-EADDRINUSE</constant></term> | |
194 | ||
d97eac36 LP |
195 | <listitem><para>It was attempted to release a name that is owned by a different peer on the |
196 | bus.</para></listitem> | |
798d3a52 ZJS |
197 | </varlistentry> |
198 | ||
199 | <varlistentry> | |
200 | <term><constant>-EINVAL</constant></term> | |
201 | ||
d97eac36 LP |
202 | <listitem><para>A specified parameter is invalid. This is also generated when the requested name is a special |
203 | service name reserved by the D-Bus specification, or when the operation is requested on a connection that does | |
204 | not refer to a bus.</para></listitem> | |
798d3a52 ZJS |
205 | </varlistentry> |
206 | ||
207 | <varlistentry> | |
208 | <term><constant>-ENOTCONN</constant></term> | |
209 | ||
d97eac36 | 210 | <listitem><para>The bus connection has been disconnected.</para></listitem> |
798d3a52 ZJS |
211 | </varlistentry> |
212 | ||
213 | <varlistentry> | |
214 | <term><constant>-ECHILD</constant></term> | |
215 | ||
d97eac36 LP |
216 | <listitem><para>The bus connection has been created in a different process than the current |
217 | one.</para></listitem> | |
798d3a52 ZJS |
218 | </varlistentry> |
219 | </variablelist> | |
220 | </refsect1> | |
221 | ||
222 | <refsect1> | |
223 | <title>Notes</title> | |
224 | ||
d97eac36 LP |
225 | <para>The <function>sd_bus_acquire_name()</function> and the other interfaces described here are available as a |
226 | shared library, which can be compiled and linked to with the <constant>libsystemd</constant> <citerefentry | |
227 | project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> file.</para> | |
798d3a52 ZJS |
228 | </refsect1> |
229 | ||
230 | <refsect1> | |
231 | <title>See Also</title> | |
232 | ||
233 | <para> | |
234 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
235 | <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
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236 | <citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
237 | <citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
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238 | </para> |
239 | </refsect1> | |
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240 | |
241 | </refentry> |