1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
|
<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
SPDX-License-Identifier: LGPL-2.1+
-->
<refentry id="sd_bus_request_name">
<refentryinfo>
<title>sd_bus_request_name</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>Developer</contrib>
<firstname>Lennart</firstname>
<surname>Poettering</surname>
<email>lennart@poettering.net</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>sd_bus_request_name</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>sd_bus_request_name</refname>
<refname>sd_bus_request_name_async</refname>
<refname>sd_bus_release_name</refname>
<refname>sd_bus_release_name_async</refname>
<refpurpose>Request or release a well-known service name on a bus</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
<funcprototype>
<funcdef>int <function>sd_bus_request_name</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>const char *<parameter>name</parameter></paramdef>
<paramdef>uint64_t <parameter>flags</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_bus_request_name_async</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef>
<paramdef>const char *<parameter>name</parameter></paramdef>
<paramdef>uint64_t <parameter>flags</parameter></paramdef>
<paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef>
<paramdef>void *<parameter>userdata</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_bus_release_name</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>const char *<parameter>name</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_bus_release_name_async</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef>
<paramdef>const char *<parameter>name</parameter></paramdef>
<paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef>
<paramdef>void *<parameter>userdata</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><function>sd_bus_request_name()</function> requests a well-known service name on a bus. It takes a bus
connection, a valid bus name and a flags parameter. The flags parameter is a combination of the following
flags:</para>
<variablelist>
<varlistentry>
<term><varname>SD_BUS_NAME_ALLOW_REPLACEMENT</varname></term>
<listitem><para>After acquiring the name successfully, permit other peers to take over the name when they try
to acquire it with the <varname>SD_BUS_NAME_REPLACE_EXISTING</varname> flag set. If
<varname>SD_BUS_NAME_ALLOW_REPLACEMENT</varname> is not set on the original request, such a request by other
peers will be denied.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>SD_BUS_NAME_REPLACE_EXISTING</varname></term>
<listitem><para>Take over the name if it is already acquired by another peer, and that other peer has permitted
takeover by setting <varname>SD_BUS_NAME_ALLOW_REPLACEMENT</varname> while acquiring it.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>SD_BUS_NAME_QUEUE</varname></term>
<listitem><para>Queue the acquisition of the name when the name is already taken.</para></listitem>
</varlistentry>
</variablelist>
<para><function>sd_bus_request_name()</function> operates in a synchronous fashion: a message requesting the name
is sent to the bus broker, and the call waits until the broker responds.</para>
<para><function>sd_bus_request_name_async()</function> is an asynchronous version of
<function>sd_bus_release_name()</function>. Instead of waiting for the request to complete, the request message is
enqueued. The specified <parameter>callback</parameter> will be called when the broker's response is received. If
the parameter is specified as <constant>NULL</constant> a default implementation is used instead which will
terminate the connection when the name cannot be acquired. The function returns a slot object in its
<parameter>slot</parameter> parameter — if it is passed as non-<constant>NULL</constant> — which may be used as a
reference to the name request operation. Use
<citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> to destroy
this reference. Note that destroying the reference will not unregister the name, but simply ensure the specified
callback is no longer called.</para>
<para><function>sd_bus_release_name()</function> releases an acquired well-known name. It takes a bus connection
and a valid bus name as parameters. This function operates synchronously, sending a release request message to the
bus broker and waiting for it to reply.</para>
<para><function>sd_bus_release_name_async()</function> is an asynchronous version of
<function>sd_bus_release_name()</function>. The specified <parameter>callback</parameter> function is called when
the name has been released successfully. If specified as <constant>NULL</constant> a generic implementation is used
that ignores the result of the operation. As above, the <parameter>slot</parameter> (if
non-<constant>NULL</constant>) is set to an object that may be used to reference the operation.</para>
<para>These functions are supported only on bus connections, i.e. connections to a bus broker and not on direct
connections.</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para>On success, these calls return 0 or a positive integer. On failure, these calls return a negative errno-style
error code.</para>
<para>If <varname>SD_BUS_NAME_QUEUE</varname> is specified, <function>sd_bus_request_name()</function> will return
0 when the name is already taken by another peer and the client has been added to the queue for the name. In that
case, the caller can subscribe to <literal>NameOwnerChanged</literal> signals to be notified when the name is
successfully acquired. <function>sd_bus_request_name()</function> returns > 0 when the name has immediately
been acquired successfully.</para>
</refsect1>
<refsect1>
<title>Errors</title>
<para>Returned errors may indicate the following problems:</para>
<variablelist>
<varlistentry>
<term><constant>-EALREADY</constant></term>
<listitem><para>The caller already is the owner of the specified name.</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>-EEXIST</constant></term>
<listitem><para>The name has already been acquired by a different peer, and SD_BUS_NAME_REPLACE_EXISTING was
not specified or the other peer did not specify SD_BUS_NAME_ALLOW_REPLACEMENT while acquiring the
name.</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>-ESRCH</constant></term>
<listitem><para>It was attempted to release a name that is currently not registered on the
bus.</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>-EADDRINUSE</constant></term>
<listitem><para>It was attempted to release a name that is owned by a different peer on the
bus.</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>-EINVAL</constant></term>
<listitem><para>A specified parameter is invalid. This is also generated when the requested name is a special
service name reserved by the D-Bus specification, or when the operation is requested on a connection that does
not refer to a bus.</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>-ENOTCONN</constant></term>
<listitem><para>The bus connection has been disconnected.</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>-ECHILD</constant></term>
<listitem><para>The bus connection has been created in a different process than the current
one.</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Notes</title>
<para>The <function>sd_bus_acquire_name()</function> and the other interfaces described here are available as a
shared library, which can be compiled and linked to with the <constant>libsystemd</constant> <citerefentry
project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> file.</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
|
