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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+ --> | |
5 | ||
6 | <refentry id="sd_bus_request_name" | |
7 | xmlns:xi="http://www.w3.org/2001/XInclude"> | |
8 | ||
9 | <refentryinfo> | |
10 | <title>sd_bus_request_name</title> | |
11 | <productname>systemd</productname> | |
12 | </refentryinfo> | |
13 | ||
14 | <refmeta> | |
15 | <refentrytitle>sd_bus_request_name</refentrytitle> | |
16 | <manvolnum>3</manvolnum> | |
17 | </refmeta> | |
18 | ||
19 | <refnamediv> | |
20 | <refname>sd_bus_request_name</refname> | |
21 | <refname>sd_bus_request_name_async</refname> | |
22 | <refname>sd_bus_release_name</refname> | |
23 | <refname>sd_bus_release_name_async</refname> | |
24 | <refpurpose>Request or release a well-known service name on a bus</refpurpose> | |
25 | </refnamediv> | |
26 | ||
27 | <refsynopsisdiv> | |
28 | <funcsynopsis> | |
29 | <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> | |
30 | ||
31 | <funcprototype> | |
32 | <funcdef>int <function>sd_bus_request_name</function></funcdef> | |
33 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> | |
34 | <paramdef>const char *<parameter>name</parameter></paramdef> | |
35 | <paramdef>uint64_t <parameter>flags</parameter></paramdef> | |
36 | </funcprototype> | |
37 | ||
38 | <funcprototype> | |
39 | <funcdef>int <function>sd_bus_request_name_async</function></funcdef> | |
40 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> | |
41 | <paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef> | |
42 | <paramdef>const char *<parameter>name</parameter></paramdef> | |
43 | <paramdef>uint64_t <parameter>flags</parameter></paramdef> | |
44 | <paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef> | |
45 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
46 | </funcprototype> | |
47 | ||
48 | <funcprototype> | |
49 | <funcdef>int <function>sd_bus_release_name</function></funcdef> | |
50 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> | |
51 | <paramdef>const char *<parameter>name</parameter></paramdef> | |
52 | </funcprototype> | |
53 | ||
54 | <funcprototype> | |
55 | <funcdef>int <function>sd_bus_release_name_async</function></funcdef> | |
56 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> | |
57 | <paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef> | |
58 | <paramdef>const char *<parameter>name</parameter></paramdef> | |
59 | <paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef> | |
60 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
61 | </funcprototype> | |
62 | </funcsynopsis> | |
63 | </refsynopsisdiv> | |
64 | ||
65 | <refsect1> | |
66 | <title>Description</title> | |
67 | ||
68 | <para><function>sd_bus_request_name()</function> requests a well-known service name on a bus. It takes a | |
69 | bus connection, a valid bus name, and a flags parameter. The flags parameter is a combination of zero or | |
70 | more of the following flags:</para> | |
71 | ||
72 | <variablelist> | |
73 | <varlistentry> | |
74 | <term><constant>SD_BUS_NAME_ALLOW_REPLACEMENT</constant></term> | |
75 | ||
76 | <listitem><para>After acquiring the name successfully, permit other peers to take over the name when they try | |
77 | to acquire it with the <constant>SD_BUS_NAME_REPLACE_EXISTING</constant> flag set. If | |
78 | <constant>SD_BUS_NAME_ALLOW_REPLACEMENT</constant> is not set on the original request, such a request by other | |
79 | peers will be denied.</para></listitem> | |
80 | </varlistentry> | |
81 | ||
82 | <varlistentry> | |
83 | <term><constant>SD_BUS_NAME_REPLACE_EXISTING</constant></term> | |
84 | ||
85 | <listitem><para>Take over the name if it was already acquired by another peer, and that other peer | |
86 | has permitted takeover by setting <constant>SD_BUS_NAME_ALLOW_REPLACEMENT</constant> while acquiring | |
87 | it.</para></listitem> | |
88 | </varlistentry> | |
89 | ||
90 | <varlistentry> | |
91 | <term><constant>SD_BUS_NAME_QUEUE</constant></term> | |
92 | ||
93 | <listitem><para>Queue the acquisition of the name when the name is already taken.</para></listitem> | |
94 | </varlistentry> | |
95 | </variablelist> | |
96 | ||
97 | <para><function>sd_bus_request_name()</function> operates in a synchronous fashion: a message requesting the name | |
98 | is sent to the bus broker, and the call waits until the broker responds.</para> | |
99 | ||
100 | <para><function>sd_bus_request_name_async()</function> is an asynchronous version of | |
101 | <function>sd_bus_release_name()</function>. Instead of waiting for the request to complete, the request message is | |
102 | enqueued. The specified <parameter>callback</parameter> will be called when the broker's response is received. If | |
103 | the parameter is specified as <constant>NULL</constant> a default implementation is used instead which will | |
104 | terminate the connection when the name cannot be acquired. The function returns a slot object in its | |
105 | <parameter>slot</parameter> parameter — if it is passed as non-<constant>NULL</constant> — which may be used as a | |
106 | reference to the name request operation. Use | |
107 | <citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> to destroy | |
108 | this reference. Note that destroying the reference will not unregister the name, but simply ensure the specified | |
109 | callback is no longer called.</para> | |
110 | ||
111 | <para><function>sd_bus_release_name()</function> releases an acquired well-known name. It takes a bus connection | |
112 | and a valid bus name as parameters. This function operates synchronously, sending a release request message to the | |
113 | bus broker and waiting for it to reply.</para> | |
114 | ||
115 | <para><function>sd_bus_release_name_async()</function> is an asynchronous version of | |
116 | <function>sd_bus_release_name()</function>. The specified <parameter>callback</parameter> function is called when | |
117 | the name has been released successfully. If specified as <constant>NULL</constant> a generic implementation is used | |
118 | that ignores the result of the operation. As above, the <parameter>slot</parameter> (if | |
119 | non-<constant>NULL</constant>) is set to an object that may be used to reference the operation.</para> | |
120 | ||
121 | <para>These functions are supported only on bus connections, i.e. connections to a bus broker and not on direct | |
122 | connections.</para> | |
123 | </refsect1> | |
124 | ||
125 | <refsect1> | |
126 | <title>Return Value</title> | |
127 | ||
128 | <para>On success, these calls return 0 or a positive integer. On failure, these calls return a negative errno-style | |
129 | error code.</para> | |
130 | ||
131 | <para>If <constant>SD_BUS_NAME_QUEUE</constant> is specified, <function>sd_bus_request_name()</function> will return | |
132 | 0 when the name is already taken by another peer and the client has been added to the queue for the name. In that | |
133 | case, the caller can subscribe to <literal>NameOwnerChanged</literal> signals to be notified when the name is | |
134 | successfully acquired. <function>sd_bus_request_name()</function> returns > 0 when the name has immediately | |
135 | been acquired successfully.</para> | |
136 | ||
137 | <refsect2> | |
138 | <title>Errors</title> | |
139 | ||
140 | <para>Returned errors may indicate the following problems:</para> | |
141 | ||
142 | <variablelist> | |
143 | <varlistentry> | |
144 | <term><constant>-EALREADY</constant></term> | |
145 | ||
146 | <listitem><para>The caller already is the owner of the specified name.</para></listitem> | |
147 | </varlistentry> | |
148 | ||
149 | <varlistentry> | |
150 | <term><constant>-EEXIST</constant></term> | |
151 | ||
152 | <listitem><para>The name has already been acquired by a different peer, and SD_BUS_NAME_REPLACE_EXISTING was | |
153 | not specified or the other peer did not specify SD_BUS_NAME_ALLOW_REPLACEMENT while acquiring the | |
154 | name.</para></listitem> | |
155 | </varlistentry> | |
156 | ||
157 | <varlistentry> | |
158 | <term><constant>-ESRCH</constant></term> | |
159 | ||
160 | <listitem><para>It was attempted to release a name that is currently not registered on the | |
161 | bus.</para></listitem> | |
162 | </varlistentry> | |
163 | ||
164 | <varlistentry> | |
165 | <term><constant>-EADDRINUSE</constant></term> | |
166 | ||
167 | <listitem><para>It was attempted to release a name that is owned by a different peer on the | |
168 | bus.</para></listitem> | |
169 | </varlistentry> | |
170 | ||
171 | <varlistentry> | |
172 | <term><constant>-EINVAL</constant></term> | |
173 | ||
174 | <listitem><para>A specified parameter is invalid. This is also generated when the requested name is | |
175 | a special service name reserved by the D-Bus specification, or when the operation is requested on a | |
176 | connection that does not refer to a bus.</para></listitem> | |
177 | </varlistentry> | |
178 | ||
179 | <varlistentry> | |
180 | <term><constant>-ENOTCONN</constant></term> | |
181 | ||
182 | <listitem><para>The bus connection has been disconnected.</para></listitem> | |
183 | </varlistentry> | |
184 | ||
185 | <varlistentry> | |
186 | <term><constant>-ECHILD</constant></term> | |
187 | ||
188 | <listitem><para>The bus connection has been created in a different process than the current | |
189 | one.</para></listitem> | |
190 | </varlistentry> | |
191 | </variablelist> | |
192 | </refsect2> | |
193 | </refsect1> | |
194 | ||
195 | <xi:include href="libsystemd-pkgconfig.xml" /> | |
196 | ||
197 | <refsect1> | |
198 | <title>See Also</title> | |
199 | ||
200 | <para> | |
201 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
202 | <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
203 | <citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
204 | <citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
205 | </para> | |
206 | </refsect1> | |
207 | ||
208 | </refentry> |