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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 | 6 | SPDX-License-Identifier: LGPL-2.1+ |
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7 | --> |
8 | ||
48f69d8f | 9 | <refentry id="sd_bus_request_name"> |
e7176abb | 10 | |
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11 | <refentryinfo> |
12 | <title>sd_bus_request_name</title> | |
13 | <productname>systemd</productname> | |
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14 | </refentryinfo> |
15 | ||
16 | <refmeta> | |
17 | <refentrytitle>sd_bus_request_name</refentrytitle> | |
18 | <manvolnum>3</manvolnum> | |
19 | </refmeta> | |
20 | ||
21 | <refnamediv> | |
22 | <refname>sd_bus_request_name</refname> | |
d97eac36 | 23 | <refname>sd_bus_request_name_async</refname> |
798d3a52 | 24 | <refname>sd_bus_release_name</refname> |
d97eac36 | 25 | <refname>sd_bus_release_name_async</refname> |
2a2e6a08 | 26 | <refpurpose>Request or release a well-known service name on a bus</refpurpose> |
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27 | </refnamediv> |
28 | ||
29 | <refsynopsisdiv> | |
30 | <funcsynopsis> | |
31 | <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> | |
32 | ||
33 | <funcprototype> | |
34 | <funcdef>int <function>sd_bus_request_name</function></funcdef> | |
35 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> | |
36 | <paramdef>const char *<parameter>name</parameter></paramdef> | |
37 | <paramdef>uint64_t <parameter>flags</parameter></paramdef> | |
38 | </funcprototype> | |
39 | ||
d97eac36 LP |
40 | <funcprototype> |
41 | <funcdef>int <function>sd_bus_request_name_async</function></funcdef> | |
42 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> | |
43 | <paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef> | |
44 | <paramdef>const char *<parameter>name</parameter></paramdef> | |
45 | <paramdef>uint64_t <parameter>flags</parameter></paramdef> | |
46 | <paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef> | |
47 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
48 | </funcprototype> | |
49 | ||
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50 | <funcprototype> |
51 | <funcdef>int <function>sd_bus_release_name</function></funcdef> | |
52 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> | |
53 | <paramdef>const char *<parameter>name</parameter></paramdef> | |
54 | </funcprototype> | |
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55 | |
56 | <funcprototype> | |
57 | <funcdef>int <function>sd_bus_release_name_async</function></funcdef> | |
58 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> | |
59 | <paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef> | |
60 | <paramdef>const char *<parameter>name</parameter></paramdef> | |
61 | <paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef> | |
62 | <paramdef>void *<parameter>userdata</parameter></paramdef> | |
63 | </funcprototype> | |
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64 | </funcsynopsis> |
65 | </refsynopsisdiv> | |
66 | ||
67 | <refsect1> | |
68 | <title>Description</title> | |
69 | ||
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70 | <para><function>sd_bus_request_name()</function> requests a well-known service name on a bus. It takes a bus |
71 | connection, a valid bus name and a flags parameter. The flags parameter is a combination of the following | |
72 | flags:</para> | |
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73 | |
74 | <variablelist> | |
75 | <varlistentry> | |
76 | <term><varname>SD_BUS_NAME_ALLOW_REPLACEMENT</varname></term> | |
77 | ||
d97eac36 LP |
78 | <listitem><para>After acquiring the name successfully, permit other peers to take over the name when they try |
79 | to acquire it with the <varname>SD_BUS_NAME_REPLACE_EXISTING</varname> flag set. If | |
80 | <varname>SD_BUS_NAME_ALLOW_REPLACEMENT</varname> is not set on the original request, such a request by other | |
81 | peers will be denied.</para></listitem> | |
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82 | </varlistentry> |
83 | ||
84 | <varlistentry> | |
85 | <term><varname>SD_BUS_NAME_REPLACE_EXISTING</varname></term> | |
86 | ||
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87 | <listitem><para>Take over the name if it is already acquired by another peer, and that other peer has permitted |
88 | takeover by setting <varname>SD_BUS_NAME_ALLOW_REPLACEMENT</varname> while acquiring it.</para></listitem> | |
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89 | </varlistentry> |
90 | ||
91 | <varlistentry> | |
92 | <term><varname>SD_BUS_NAME_QUEUE</varname></term> | |
93 | ||
d97eac36 | 94 | <listitem><para>Queue the acquisition of the name when the name is already taken.</para></listitem> |
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95 | </varlistentry> |
96 | </variablelist> | |
97 | ||
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98 | <para><function>sd_bus_request_name()</function> operates in a synchronous fashion: a message requesting the name |
99 | is sent to the bus broker, and the call waits until the broker responds.</para> | |
100 | ||
1b2ad5d9 | 101 | <para><function>sd_bus_request_name_async()</function> is an asynchronous version of |
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102 | <function>sd_bus_release_name()</function>. Instead of waiting for the request to complete, the request message is |
103 | enqueued. The specified <parameter>callback</parameter> will be called when the broker's response is received. If | |
104 | the parameter is specified as <constant>NULL</constant> a default implementation is used instead which will | |
105 | terminate the connection when the name cannot be acquired. The function returns a slot object in its | |
106 | <parameter>slot</parameter> parameter — if it is passed as non-<constant>NULL</constant> — which may be used as a | |
107 | reference to the name request operation. Use | |
108 | <citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> to destroy | |
109 | this reference. Note that destroying the reference will not unregister the name, but simply ensure the specified | |
110 | callback is no longer called.</para> | |
111 | ||
112 | <para><function>sd_bus_release_name()</function> releases an acquired well-known name. It takes a bus connection | |
113 | and a valid bus name as parameters. This function operates synchronously, sending a release request message to the | |
114 | bus broker and waiting for it to reply.</para> | |
115 | ||
116 | <para><function>sd_bus_release_name_async()</function> is an asynchronous version of | |
117 | <function>sd_bus_release_name()</function>. The specified <parameter>callback</parameter> function is called when | |
118 | the name has been released successfully. If specified as <constant>NULL</constant> a generic implementation is used | |
119 | that ignores the result of the operation. As above, the <parameter>slot</parameter> (if | |
120 | non-<constant>NULL</constant>) is set to an object that may be used to reference the operation.</para> | |
121 | ||
122 | <para>These functions are supported only on bus connections, i.e. connections to a bus broker and not on direct | |
123 | connections.</para> | |
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124 | </refsect1> |
125 | ||
126 | <refsect1> | |
127 | <title>Return Value</title> | |
128 | ||
d97eac36 LP |
129 | <para>On success, these calls return 0 or a positive integer. On failure, these calls return a negative errno-style |
130 | error code.</para> | |
131 | ||
132 | <para>If <varname>SD_BUS_NAME_QUEUE</varname> is specified, <function>sd_bus_request_name()</function> will return | |
133 | 0 when the name is already taken by another peer and the client has been added to the queue for the name. In that | |
134 | case, the caller can subscribe to <literal>NameOwnerChanged</literal> signals to be notified when the name is | |
135 | successfully acquired. <function>sd_bus_request_name()</function> returns > 0 when the name has immediately | |
136 | been acquired successfully.</para> | |
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137 | </refsect1> |
138 | ||
139 | <refsect1> | |
140 | <title>Errors</title> | |
141 | ||
142 | <para>Returned errors may indicate the following problems:</para> | |
143 | ||
144 | <variablelist> | |
145 | <varlistentry> | |
146 | <term><constant>-EALREADY</constant></term> | |
147 | ||
d97eac36 | 148 | <listitem><para>The caller already is the owner of the specified name.</para></listitem> |
798d3a52 ZJS |
149 | </varlistentry> |
150 | ||
151 | <varlistentry> | |
152 | <term><constant>-EEXIST</constant></term> | |
153 | ||
d97eac36 LP |
154 | <listitem><para>The name has already been acquired by a different peer, and SD_BUS_NAME_REPLACE_EXISTING was |
155 | not specified or the other peer did not specify SD_BUS_NAME_ALLOW_REPLACEMENT while acquiring the | |
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156 | name.</para></listitem> |
157 | </varlistentry> | |
158 | ||
159 | <varlistentry> | |
160 | <term><constant>-ESRCH</constant></term> | |
161 | ||
d97eac36 LP |
162 | <listitem><para>It was attempted to release a name that is currently not registered on the |
163 | bus.</para></listitem> | |
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164 | </varlistentry> |
165 | ||
166 | <varlistentry> | |
167 | <term><constant>-EADDRINUSE</constant></term> | |
168 | ||
d97eac36 LP |
169 | <listitem><para>It was attempted to release a name that is owned by a different peer on the |
170 | bus.</para></listitem> | |
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171 | </varlistentry> |
172 | ||
173 | <varlistentry> | |
174 | <term><constant>-EINVAL</constant></term> | |
175 | ||
d97eac36 LP |
176 | <listitem><para>A specified parameter is invalid. This is also generated when the requested name is a special |
177 | service name reserved by the D-Bus specification, or when the operation is requested on a connection that does | |
178 | not refer to a bus.</para></listitem> | |
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179 | </varlistentry> |
180 | ||
181 | <varlistentry> | |
182 | <term><constant>-ENOTCONN</constant></term> | |
183 | ||
d97eac36 | 184 | <listitem><para>The bus connection has been disconnected.</para></listitem> |
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185 | </varlistentry> |
186 | ||
187 | <varlistentry> | |
188 | <term><constant>-ECHILD</constant></term> | |
189 | ||
d97eac36 LP |
190 | <listitem><para>The bus connection has been created in a different process than the current |
191 | one.</para></listitem> | |
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192 | </varlistentry> |
193 | </variablelist> | |
194 | </refsect1> | |
195 | ||
196 | <refsect1> | |
197 | <title>Notes</title> | |
198 | ||
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199 | <para>The <function>sd_bus_acquire_name()</function> and the other interfaces described here are available as a |
200 | shared library, which can be compiled and linked to with the <constant>libsystemd</constant> <citerefentry | |
201 | project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> file.</para> | |
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202 | </refsect1> |
203 | ||
204 | <refsect1> | |
205 | <title>See Also</title> | |
206 | ||
207 | <para> | |
208 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
209 | <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
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210 | <citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
211 | <citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
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212 | </para> |
213 | </refsect1> | |
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214 | |
215 | </refentry> |