1 <?xml version='
1.0'
?> <!--*-nxml-*-->
2 <!DOCTYPE refentry PUBLIC
"-//OASIS//DTD DocBook XML V4.5//EN"
3 "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
4 <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
6 <refentry id=
"sd_bus_request_name"
7 xmlns:
xi=
"http://www.w3.org/2001/XInclude">
10 <title>sd_bus_request_name
</title>
11 <productname>systemd
</productname>
15 <refentrytitle>sd_bus_request_name
</refentrytitle>
16 <manvolnum>3</manvolnum>
20 <refname>sd_bus_request_name
</refname>
21 <refname>sd_bus_request_name_async
</refname>
22 <refname>sd_bus_release_name
</refname>
23 <refname>sd_bus_release_name_async
</refname>
24 <refpurpose>Request or release a well-known service name on a bus
</refpurpose>
29 <funcsynopsisinfo>#include
<systemd/sd-bus.h
></funcsynopsisinfo>
31 <xi:include href=
"sd_bus_add_match.xml" xpointer=
"sd_bus_message_handler_t"/>
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>
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>
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>
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>
68 <title>Description
</title>
70 <para><function>sd_bus_request_name()
</function> requests a well-known service name on a bus. It takes a
71 bus connection, a valid bus name, and a flags parameter. The flags parameter is a combination of zero or
72 more of the following flags:
</para>
76 <term><constant>SD_BUS_NAME_ALLOW_REPLACEMENT
</constant></term>
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
<constant>SD_BUS_NAME_REPLACE_EXISTING
</constant> flag set. If
80 <constant>SD_BUS_NAME_ALLOW_REPLACEMENT
</constant> is not set on the original request, such a request by other
81 peers will be denied.
</para>
83 <xi:include href=
"version-info.xml" xpointer=
"v209"/></listitem>
87 <term><constant>SD_BUS_NAME_REPLACE_EXISTING
</constant></term>
89 <listitem><para>Take over the name if it was already acquired by another peer, and that other peer
90 has permitted takeover by setting
<constant>SD_BUS_NAME_ALLOW_REPLACEMENT
</constant> while acquiring
93 <xi:include href=
"version-info.xml" xpointer=
"v209"/></listitem>
97 <term><constant>SD_BUS_NAME_QUEUE
</constant></term>
99 <listitem><para>Queue the acquisition of the name when the name is already taken.
</para>
101 <xi:include href=
"version-info.xml" xpointer=
"v209"/></listitem>
105 <para><function>sd_bus_request_name()
</function> operates in a synchronous fashion: a message requesting the name
106 is sent to the bus broker, and the call waits until the broker responds.
</para>
108 <para><function>sd_bus_request_name_async()
</function> is an asynchronous version of
109 <function>sd_bus_request_name()
</function>. Instead of waiting for the request to complete, the request message is
110 enqueued. The specified
<parameter>callback
</parameter> will be called when the broker's response is received. If
111 the parameter is specified as
<constant>NULL
</constant> a default implementation is used instead which will
112 terminate the connection when the name cannot be acquired. The function returns a slot object in its
113 <parameter>slot
</parameter> parameter — if it is passed as non-
<constant>NULL
</constant> — which may be used as a
114 reference to the name request operation. Use
115 <citerefentry><refentrytitle>sd_bus_slot_unref
</refentrytitle><manvolnum>3</manvolnum></citerefentry> to destroy
116 this reference. Note that destroying the reference will not unregister the name, but simply ensure the specified
117 callback is no longer called.
</para>
119 <para><function>sd_bus_release_name()
</function> releases an acquired well-known name. It takes a bus connection
120 and a valid bus name as parameters. This function operates synchronously, sending a release request message to the
121 bus broker and waiting for it to reply.
</para>
123 <para><function>sd_bus_release_name_async()
</function> is an asynchronous version of
124 <function>sd_bus_release_name()
</function>. The specified
<parameter>callback
</parameter> function is called when
125 the name has been released successfully. If specified as
<constant>NULL
</constant> a generic implementation is used
126 that ignores the result of the operation. As above, the
<parameter>slot
</parameter> (if
127 non-
<constant>NULL
</constant>) is set to an object that may be used to reference the operation.
</para>
129 <para>These functions are supported only on bus connections, i.e. connections to a bus broker and not on direct
134 <title>Return Value
</title>
136 <para>On success, these calls return
0 or a positive integer. On failure, these calls return a negative errno-style
139 <para>If
<constant>SD_BUS_NAME_QUEUE
</constant> is specified,
<function>sd_bus_request_name()
</function> will return
140 0 when the name is already taken by another peer and the client has been added to the queue for the name. In that
141 case, the caller can subscribe to
<literal>NameOwnerChanged
</literal> signals to be notified when the name is
142 successfully acquired.
<function>sd_bus_request_name()
</function> returns
> 0 when the name has immediately
143 been acquired successfully.
</para>
146 <title>Errors
</title>
148 <para>Returned errors may indicate the following problems:
</para>
152 <term><constant>-EALREADY
</constant></term>
154 <listitem><para>The caller already is the owner of the specified name.
</para></listitem>
158 <term><constant>-EEXIST
</constant></term>
160 <listitem><para>The name has already been acquired by a different peer, and SD_BUS_NAME_REPLACE_EXISTING was
161 not specified or the other peer did not specify SD_BUS_NAME_ALLOW_REPLACEMENT while acquiring the
162 name.
</para></listitem>
166 <term><constant>-ESRCH
</constant></term>
168 <listitem><para>It was attempted to release a name that is currently not registered on the
169 bus.
</para></listitem>
173 <term><constant>-EADDRINUSE
</constant></term>
175 <listitem><para>It was attempted to release a name that is owned by a different peer on the
176 bus.
</para></listitem>
180 <term><constant>-EINVAL
</constant></term>
182 <listitem><para>A specified parameter is invalid. This is also generated when the requested name is
183 a special service name reserved by the D-Bus specification, or when the operation is requested on a
184 connection that does not refer to a bus.
</para></listitem>
188 <term><constant>-ENOTCONN
</constant></term>
190 <listitem><para>The bus connection has been disconnected.
</para></listitem>
194 <term><constant>-ECHILD
</constant></term>
196 <listitem><para>The bus connection has been created in a different process than the current
197 one.
</para></listitem>
203 <xi:include href=
"libsystemd-pkgconfig.xml" />
206 <title>History
</title>
207 <para><function>sd_bus_request_name()
</function> and
208 <function>sd_bus_release_name()
</function> were added in version
209.
</para>
209 <para><function>sd_bus_request_name_async()
</function> and
210 <function>sd_bus_release_name_async()
</function> were added in version
237.
</para>
214 <title>See Also
</title>
216 <para><simplelist type=
"inline">
217 <member><citerefentry><refentrytitle>systemd
</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
218 <member><citerefentry><refentrytitle>sd-bus
</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
219 <member><citerefentry><refentrytitle>sd_bus_new
</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
220 <member><citerefentry><refentrytitle>sd_bus_slot_unref
</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>