1 <?xml version='1.0'?> <!--*-nxml-*-->
2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
6 SPDX-License-Identifier: LGPL-2.1+
8 This file is part of systemd.
10 Copyright 2013 Lennart Poettering
13 <refentry id="sd_bus_request_name">
16 <title>sd_bus_request_name</title>
17 <productname>systemd</productname>
21 <contrib>Developer</contrib>
22 <firstname>Lennart</firstname>
23 <surname>Poettering</surname>
24 <email>lennart@poettering.net</email>
30 <refentrytitle>sd_bus_request_name</refentrytitle>
31 <manvolnum>3</manvolnum>
35 <refname>sd_bus_request_name</refname>
36 <refname>sd_bus_request_name_async</refname>
37 <refname>sd_bus_release_name</refname>
38 <refname>sd_bus_release_name_async</refname>
39 <refpurpose>Request or release a well-known service name on a bus</refpurpose>
44 <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
47 <funcdef>int <function>sd_bus_request_name</function></funcdef>
48 <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
49 <paramdef>const char *<parameter>name</parameter></paramdef>
50 <paramdef>uint64_t <parameter>flags</parameter></paramdef>
54 <funcdef>int <function>sd_bus_request_name_async</function></funcdef>
55 <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
56 <paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef>
57 <paramdef>const char *<parameter>name</parameter></paramdef>
58 <paramdef>uint64_t <parameter>flags</parameter></paramdef>
59 <paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef>
60 <paramdef>void *<parameter>userdata</parameter></paramdef>
64 <funcdef>int <function>sd_bus_release_name</function></funcdef>
65 <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
66 <paramdef>const char *<parameter>name</parameter></paramdef>
70 <funcdef>int <function>sd_bus_release_name_async</function></funcdef>
71 <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
72 <paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef>
73 <paramdef>const char *<parameter>name</parameter></paramdef>
74 <paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef>
75 <paramdef>void *<parameter>userdata</parameter></paramdef>
81 <title>Description</title>
83 <para><function>sd_bus_request_name()</function> requests a well-known service name on a bus. It takes a bus
84 connection, a valid bus name and a flags parameter. The flags parameter is a combination of the following
89 <term><varname>SD_BUS_NAME_ALLOW_REPLACEMENT</varname></term>
91 <listitem><para>After acquiring the name successfully, permit other peers to take over the name when they try
92 to acquire it with the <varname>SD_BUS_NAME_REPLACE_EXISTING</varname> flag set. If
93 <varname>SD_BUS_NAME_ALLOW_REPLACEMENT</varname> is not set on the original request, such a request by other
94 peers will be denied.</para></listitem>
98 <term><varname>SD_BUS_NAME_REPLACE_EXISTING</varname></term>
100 <listitem><para>Take over the name if it is already acquired by another peer, and that other peer has permitted
101 takeover by setting <varname>SD_BUS_NAME_ALLOW_REPLACEMENT</varname> while acquiring it.</para></listitem>
105 <term><varname>SD_BUS_NAME_QUEUE</varname></term>
107 <listitem><para>Queue the acquisition of the name when the name is already taken.</para></listitem>
111 <para><function>sd_bus_request_name()</function> operates in a synchronous fashion: a message requesting the name
112 is sent to the bus broker, and the call waits until the broker responds.</para>
114 <para><function>sd_bus_request_name_async()</function> is an asynchronous version of
115 <function>sd_bus_release_name()</function>. Instead of waiting for the request to complete, the request message is
116 enqueued. The specified <parameter>callback</parameter> will be called when the broker's response is received. If
117 the parameter is specified as <constant>NULL</constant> a default implementation is used instead which will
118 terminate the connection when the name cannot be acquired. The function returns a slot object in its
119 <parameter>slot</parameter> parameter — if it is passed as non-<constant>NULL</constant> — which may be used as a
120 reference to the name request operation. Use
121 <citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> to destroy
122 this reference. Note that destroying the reference will not unregister the name, but simply ensure the specified
123 callback is no longer called.</para>
125 <para><function>sd_bus_release_name()</function> releases an acquired well-known name. It takes a bus connection
126 and a valid bus name as parameters. This function operates synchronously, sending a release request message to the
127 bus broker and waiting for it to reply.</para>
129 <para><function>sd_bus_release_name_async()</function> is an asynchronous version of
130 <function>sd_bus_release_name()</function>. The specified <parameter>callback</parameter> function is called when
131 the name has been released successfully. If specified as <constant>NULL</constant> a generic implementation is used
132 that ignores the result of the operation. As above, the <parameter>slot</parameter> (if
133 non-<constant>NULL</constant>) is set to an object that may be used to reference the operation.</para>
135 <para>These functions are supported only on bus connections, i.e. connections to a bus broker and not on direct
140 <title>Return Value</title>
142 <para>On success, these calls return 0 or a positive integer. On failure, these calls return a negative errno-style
145 <para>If <varname>SD_BUS_NAME_QUEUE</varname> is specified, <function>sd_bus_request_name()</function> will return
146 0 when the name is already taken by another peer and the client has been added to the queue for the name. In that
147 case, the caller can subscribe to <literal>NameOwnerChanged</literal> signals to be notified when the name is
148 successfully acquired. <function>sd_bus_request_name()</function> returns > 0 when the name has immediately
149 been acquired successfully.</para>
153 <title>Errors</title>
155 <para>Returned errors may indicate the following problems:</para>
159 <term><constant>-EALREADY</constant></term>
161 <listitem><para>The caller already is the owner of the specified name.</para></listitem>
165 <term><constant>-EEXIST</constant></term>
167 <listitem><para>The name has already been acquired by a different peer, and SD_BUS_NAME_REPLACE_EXISTING was
168 not specified or the other peer did not specify SD_BUS_NAME_ALLOW_REPLACEMENT while acquiring the
169 name.</para></listitem>
173 <term><constant>-ESRCH</constant></term>
175 <listitem><para>It was attempted to release a name that is currently not registered on the
176 bus.</para></listitem>
180 <term><constant>-EADDRINUSE</constant></term>
182 <listitem><para>It was attempted to release a name that is owned by a different peer on the
183 bus.</para></listitem>
187 <term><constant>-EINVAL</constant></term>
189 <listitem><para>A specified parameter is invalid. This is also generated when the requested name is a special
190 service name reserved by the D-Bus specification, or when the operation is requested on a connection that does
191 not refer to a bus.</para></listitem>
195 <term><constant>-ENOTCONN</constant></term>
197 <listitem><para>The bus connection has been disconnected.</para></listitem>
201 <term><constant>-ECHILD</constant></term>
203 <listitem><para>The bus connection has been created in a different process than the current
204 one.</para></listitem>
212 <para>The <function>sd_bus_acquire_name()</function> and the other interfaces described here are available as a
213 shared library, which can be compiled and linked to with the <constant>libelogind</constant> <citerefentry
214 project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> file.</para>
218 <title>See Also</title>
221 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
222 <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
223 <citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
224 <citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>