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e7176abb | 1 | <?xml version='1.0'?> <!--*-nxml-*--> |
3a54a157 | 2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" |
12b42c76 | 3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
0307f791 | 4 | <!-- SPDX-License-Identifier: LGPL-2.1+ --> |
e7176abb | 5 | |
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6 | <refentry id="sd_bus_request_name" |
7 | xmlns:xi="http://www.w3.org/2001/XInclude"> | |
e7176abb | 8 | |
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9 | <refentryinfo> |
10 | <title>sd_bus_request_name</title> | |
11 | <productname>systemd</productname> | |
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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> | |
d97eac36 | 21 | <refname>sd_bus_request_name_async</refname> |
798d3a52 | 22 | <refname>sd_bus_release_name</refname> |
d97eac36 | 23 | <refname>sd_bus_release_name_async</refname> |
2a2e6a08 | 24 | <refpurpose>Request or release a well-known service name on a bus</refpurpose> |
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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 | ||
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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 | ||
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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> | |
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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> | |
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62 | </funcsynopsis> |
63 | </refsynopsisdiv> | |
64 | ||
65 | <refsect1> | |
66 | <title>Description</title> | |
67 | ||
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68 | <para><function>sd_bus_request_name()</function> requests a well-known service name on a bus. It takes a bus |
69 | connection, a valid bus name and a flags parameter. The flags parameter is a combination of the following | |
70 | flags:</para> | |
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71 | |
72 | <variablelist> | |
73 | <varlistentry> | |
b6783592 | 74 | <term><constant>SD_BUS_NAME_ALLOW_REPLACEMENT</constant></term> |
798d3a52 | 75 | |
d97eac36 | 76 | <listitem><para>After acquiring the name successfully, permit other peers to take over the name when they try |
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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 | |
d97eac36 | 79 | peers will be denied.</para></listitem> |
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80 | </varlistentry> |
81 | ||
82 | <varlistentry> | |
b6783592 | 83 | <term><constant>SD_BUS_NAME_REPLACE_EXISTING</constant></term> |
798d3a52 | 84 | |
d97eac36 | 85 | <listitem><para>Take over the name if it is already acquired by another peer, and that other peer has permitted |
b6783592 | 86 | takeover by setting <constant>SD_BUS_NAME_ALLOW_REPLACEMENT</constant> while acquiring it.</para></listitem> |
798d3a52 ZJS |
87 | </varlistentry> |
88 | ||
89 | <varlistentry> | |
b6783592 | 90 | <term><constant>SD_BUS_NAME_QUEUE</constant></term> |
798d3a52 | 91 | |
d97eac36 | 92 | <listitem><para>Queue the acquisition of the name when the name is already taken.</para></listitem> |
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93 | </varlistentry> |
94 | </variablelist> | |
95 | ||
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96 | <para><function>sd_bus_request_name()</function> operates in a synchronous fashion: a message requesting the name |
97 | is sent to the bus broker, and the call waits until the broker responds.</para> | |
98 | ||
1b2ad5d9 | 99 | <para><function>sd_bus_request_name_async()</function> is an asynchronous version of |
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100 | <function>sd_bus_release_name()</function>. Instead of waiting for the request to complete, the request message is |
101 | enqueued. The specified <parameter>callback</parameter> will be called when the broker's response is received. If | |
102 | the parameter is specified as <constant>NULL</constant> a default implementation is used instead which will | |
103 | terminate the connection when the name cannot be acquired. The function returns a slot object in its | |
104 | <parameter>slot</parameter> parameter — if it is passed as non-<constant>NULL</constant> — which may be used as a | |
105 | reference to the name request operation. Use | |
106 | <citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> to destroy | |
107 | this reference. Note that destroying the reference will not unregister the name, but simply ensure the specified | |
108 | callback is no longer called.</para> | |
109 | ||
110 | <para><function>sd_bus_release_name()</function> releases an acquired well-known name. It takes a bus connection | |
111 | and a valid bus name as parameters. This function operates synchronously, sending a release request message to the | |
112 | bus broker and waiting for it to reply.</para> | |
113 | ||
114 | <para><function>sd_bus_release_name_async()</function> is an asynchronous version of | |
115 | <function>sd_bus_release_name()</function>. The specified <parameter>callback</parameter> function is called when | |
116 | the name has been released successfully. If specified as <constant>NULL</constant> a generic implementation is used | |
117 | that ignores the result of the operation. As above, the <parameter>slot</parameter> (if | |
118 | non-<constant>NULL</constant>) is set to an object that may be used to reference the operation.</para> | |
119 | ||
120 | <para>These functions are supported only on bus connections, i.e. connections to a bus broker and not on direct | |
121 | connections.</para> | |
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122 | </refsect1> |
123 | ||
124 | <refsect1> | |
125 | <title>Return Value</title> | |
126 | ||
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127 | <para>On success, these calls return 0 or a positive integer. On failure, these calls return a negative errno-style |
128 | error code.</para> | |
129 | ||
b6783592 | 130 | <para>If <constant>SD_BUS_NAME_QUEUE</constant> is specified, <function>sd_bus_request_name()</function> will return |
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131 | 0 when the name is already taken by another peer and the client has been added to the queue for the name. In that |
132 | case, the caller can subscribe to <literal>NameOwnerChanged</literal> signals to be notified when the name is | |
133 | successfully acquired. <function>sd_bus_request_name()</function> returns > 0 when the name has immediately | |
134 | been acquired successfully.</para> | |
798d3a52 | 135 | |
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136 | <refsect2> |
137 | <title>Errors</title> | |
798d3a52 | 138 | |
b1de39de | 139 | <para>Returned errors may indicate the following problems:</para> |
798d3a52 | 140 | |
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141 | <variablelist> |
142 | <varlistentry> | |
143 | <term><constant>-EALREADY</constant></term> | |
798d3a52 | 144 | |
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145 | <listitem><para>The caller already is the owner of the specified name.</para></listitem> |
146 | </varlistentry> | |
798d3a52 | 147 | |
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148 | <varlistentry> |
149 | <term><constant>-EEXIST</constant></term> | |
798d3a52 | 150 | |
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151 | <listitem><para>The name has already been acquired by a different peer, and SD_BUS_NAME_REPLACE_EXISTING was |
152 | not specified or the other peer did not specify SD_BUS_NAME_ALLOW_REPLACEMENT while acquiring the | |
153 | name.</para></listitem> | |
154 | </varlistentry> | |
798d3a52 | 155 | |
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156 | <varlistentry> |
157 | <term><constant>-ESRCH</constant></term> | |
798d3a52 | 158 | |
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159 | <listitem><para>It was attempted to release a name that is currently not registered on the |
160 | bus.</para></listitem> | |
161 | </varlistentry> | |
798d3a52 | 162 | |
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163 | <varlistentry> |
164 | <term><constant>-EADDRINUSE</constant></term> | |
798d3a52 | 165 | |
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166 | <listitem><para>It was attempted to release a name that is owned by a different peer on the |
167 | bus.</para></listitem> | |
168 | </varlistentry> | |
798d3a52 | 169 | |
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170 | <varlistentry> |
171 | <term><constant>-EINVAL</constant></term> | |
798d3a52 | 172 | |
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173 | <listitem><para>A specified parameter is invalid. This is also generated when the requested name is |
174 | a special service name reserved by the D-Bus specification, or when the operation is requested on a | |
175 | connection that does not refer to a bus.</para></listitem> | |
176 | </varlistentry> | |
798d3a52 | 177 | |
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178 | <varlistentry> |
179 | <term><constant>-ENOTCONN</constant></term> | |
798d3a52 | 180 | |
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181 | <listitem><para>The bus connection has been disconnected.</para></listitem> |
182 | </varlistentry> | |
798d3a52 | 183 | |
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184 | <varlistentry> |
185 | <term><constant>-ECHILD</constant></term> | |
798d3a52 | 186 | |
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187 | <listitem><para>The bus connection has been created in a different process than the current |
188 | one.</para></listitem> | |
189 | </varlistentry> | |
190 | </variablelist> | |
191 | </refsect2> | |
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192 | </refsect1> |
193 | ||
7647c01d | 194 | <xi:include href="libsystemd-pkgconfig.xml" /> |
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195 | |
196 | <refsect1> | |
197 | <title>See Also</title> | |
198 | ||
199 | <para> | |
200 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
201 | <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
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202 | <citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
203 | <citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
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204 | </para> |
205 | </refsect1> | |
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206 | |
207 | </refentry> |