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"-//OASIS//DTD DocBook XML V4.2//EN"
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6 SPDX-License-Identifier: LGPL-2.1+
8 This file is part of systemd.
10 Copyright 2013 Lennart Poettering
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.
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.
22 You should have received a copy of the GNU Lesser General Public License
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26 <refentry id=
"sd_bus_request_name">
29 <title>sd_bus_request_name
</title>
30 <productname>systemd
</productname>
34 <contrib>Developer
</contrib>
35 <firstname>Lennart
</firstname>
36 <surname>Poettering
</surname>
37 <email>lennart@poettering.net
</email>
43 <refentrytitle>sd_bus_request_name
</refentrytitle>
44 <manvolnum>3</manvolnum>
48 <refname>sd_bus_request_name
</refname>
49 <refname>sd_bus_request_name_async
</refname>
50 <refname>sd_bus_release_name
</refname>
51 <refname>sd_bus_release_name_async
</refname>
52 <refpurpose>Request or release a well-known service name on a bus
</refpurpose>
57 <funcsynopsisinfo>#include
<systemd/sd-bus.h
></funcsynopsisinfo>
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>
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>
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>
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>
94 <title>Description
</title>
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
102 <term><varname>SD_BUS_NAME_ALLOW_REPLACEMENT
</varname></term>
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>
111 <term><varname>SD_BUS_NAME_REPLACE_EXISTING
</varname></term>
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>
118 <term><varname>SD_BUS_NAME_QUEUE
</varname></term>
120 <listitem><para>Queue the acquisition of the name when the name is already taken.
</para></listitem>
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>
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>
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>
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>
148 <para>These functions are supported only on bus connections, i.e. connections to a bus broker and not on direct
153 <title>Return Value
</title>
155 <para>On success, these calls return
0 or a positive integer. On failure, these calls return a negative errno-style
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>
166 <title>Errors
</title>
168 <para>Returned errors may indicate the following problems:
</para>
172 <term><constant>-EALREADY
</constant></term>
174 <listitem><para>The caller already is the owner of the specified name.
</para></listitem>
178 <term><constant>-EEXIST
</constant></term>
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
182 name.
</para></listitem>
186 <term><constant>-ESRCH
</constant></term>
188 <listitem><para>It was attempted to release a name that is currently not registered on the
189 bus.
</para></listitem>
193 <term><constant>-EADDRINUSE
</constant></term>
195 <listitem><para>It was attempted to release a name that is owned by a different peer on the
196 bus.
</para></listitem>
200 <term><constant>-EINVAL
</constant></term>
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>
208 <term><constant>-ENOTCONN
</constant></term>
210 <listitem><para>The bus connection has been disconnected.
</para></listitem>
214 <term><constant>-ECHILD
</constant></term>
216 <listitem><para>The bus connection has been created in a different process than the current
217 one.
</para></listitem>
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>
231 <title>See Also
</title>
234 <citerefentry><refentrytitle>systemd
</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
235 <citerefentry><refentrytitle>sd-bus
</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
236 <citerefentry><refentrytitle>sd_bus_new
</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
237 <citerefentry><refentrytitle>sd_bus_slot_unref
</refentrytitle><manvolnum>3</manvolnum></citerefentry>