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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 &lt;systemd/sd-bus.h&gt;</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>
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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 &gt; 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>