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3802a3d3 | 1 | <?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*--> |
cd6d5e1c | 2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" |
12b42c76 | 3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
cd6d5e1c ZJS |
4 | |
5 | <!-- | |
572eb058 ZJS |
6 | SPDX-License-Identifier: LGPL-2.1+ |
7 | ||
b975b0d5 | 8 | This file is part of systemd. |
cd6d5e1c | 9 | |
b975b0d5 | 10 | Copyright 2014 Zbigniew Jędrzejewski-Szmek |
cd6d5e1c | 11 | |
b975b0d5 ZJS |
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. | |
cd6d5e1c | 16 | |
b975b0d5 ZJS |
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. | |
cd6d5e1c | 21 | |
b975b0d5 ZJS |
22 | You should have received a copy of the GNU Lesser General Public License |
23 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
cd6d5e1c ZJS |
24 | --> |
25 | ||
48f69d8f | 26 | <refentry id="sd_bus_new"> |
cd6d5e1c ZJS |
27 | |
28 | <refentryinfo> | |
29 | <title>sd_bus_new</title> | |
30 | <productname>systemd</productname> | |
31 | ||
32 | <authorgroup> | |
33 | <author> | |
34 | <contrib>A monkey with a typewriter</contrib> | |
35 | <firstname>Zbigniew</firstname> | |
36 | <surname>Jędrzejewski-Szmek</surname> | |
37 | <email>zbyszek@in.waw.pl</email> | |
38 | </author> | |
39 | </authorgroup> | |
40 | </refentryinfo> | |
41 | ||
42 | <refmeta> | |
43 | <refentrytitle>sd_bus_new</refentrytitle> | |
44 | <manvolnum>3</manvolnum> | |
45 | </refmeta> | |
46 | ||
47 | <refnamediv> | |
48 | <refname>sd_bus_new</refname> | |
49 | <refname>sd_bus_ref</refname> | |
50 | <refname>sd_bus_unref</refname> | |
4afd3348 | 51 | <refname>sd_bus_unrefp</refname> |
cd6d5e1c ZJS |
52 | |
53 | <refpurpose>Create a new bus object and create or destroy references to it</refpurpose> | |
54 | </refnamediv> | |
55 | ||
56 | <refsynopsisdiv> | |
57 | <funcsynopsis> | |
58 | <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> | |
59 | ||
60 | <funcprototype> | |
61 | <funcdef>int <function>sd_bus_new</function></funcdef> | |
8dc385e7 | 62 | <paramdef>sd_bus **<parameter>bus</parameter></paramdef> |
cd6d5e1c ZJS |
63 | </funcprototype> |
64 | ||
65 | <funcprototype> | |
8dc385e7 JE |
66 | <funcdef>sd_bus *<function>sd_bus_ref</function></funcdef> |
67 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> | |
cd6d5e1c ZJS |
68 | </funcprototype> |
69 | ||
70 | <funcprototype> | |
8dc385e7 JE |
71 | <funcdef>sd_bus *<function>sd_bus_unref</function></funcdef> |
72 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> | |
cd6d5e1c | 73 | </funcprototype> |
4afd3348 LP |
74 | |
75 | <funcprototype> | |
76 | <funcdef>void <function>sd_bus_unrefp</function></funcdef> | |
77 | <paramdef>sd_bus **<parameter>bus</parameter></paramdef> | |
78 | </funcprototype> | |
cd6d5e1c ZJS |
79 | </funcsynopsis> |
80 | </refsynopsisdiv> | |
81 | ||
82 | <refsect1> | |
83 | <title>Description</title> | |
84 | ||
85 | <para><function>sd_bus_new()</function> creates a new bus | |
73e231ab | 86 | object. This object is reference-counted, and will be destroyed |
cd6d5e1c | 87 | when all references are gone. Initially, the caller of this |
db03761e UTL |
88 | function owns the sole reference and the bus object will not be |
89 | connected to any bus. To connect it to a bus, make sure | |
850df10a LP |
90 | to set an address with |
91 | <citerefentry><refentrytitle>sd_bus_set_address</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
92 | or a related call, and then start the connection with | |
93 | <citerefentry><refentrytitle>sd_bus_start</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> | |
94 | ||
7ca41557 | 95 | <para>In most cases, it is a better idea to invoke |
850df10a LP |
96 | <citerefentry><refentrytitle>sd_bus_default_user</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
97 | <citerefentry><refentrytitle>sd_bus_default_system</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
98 | or related calls instead of the more low-level | |
99 | <function>sd_bus_new()</function> and | |
100 | <function>sd_bus_start()</function>. The higher-level calls not | |
101 | only allocate a bus object but also start the connection to a | |
102 | well-known bus in a single function invocation.</para> | |
cd6d5e1c | 103 | |
4afd3348 LP |
104 | <para><function>sd_bus_ref()</function> increases the reference |
105 | counter of <parameter>bus</parameter> by one.</para> | |
cd6d5e1c | 106 | |
4afd3348 LP |
107 | <para><function>sd_bus_unref()</function> decreases the reference |
108 | counter of <parameter>bus</parameter> by one. Once the reference | |
109 | count has dropped to zero, <parameter>bus</parameter> is destroyed | |
110 | and cannot be used anymore, so further calls to | |
111 | <function>sd_bus_ref()</function> or | |
db03761e | 112 | <function>sd_bus_unref()</function> are illegal.</para> |
4afd3348 LP |
113 | |
114 | <para><function>sd_bus_unrefp()</function> is similar to | |
115 | <function>sd_bus_unref()</function> but takes a pointer to a | |
116 | pointer to an <type>sd_bus</type> object. This call is useful in | |
117 | conjunction with GCC's and LLVM's <ulink | |
118 | url="https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up | |
119 | Variable Attribute</ulink>. Note that this function is defined as | |
120 | inline function. Use a declaration like the following, in order to | |
121 | allocate a bus object that is freed automatically as the code | |
122 | block is left:</para> | |
123 | ||
124 | <programlisting>{ | |
125 | __attribute__((cleanup(sd_bus_unrefp)) sd_bus *bus = NULL; | |
126 | int r; | |
127 | … | |
128 | r = sd_bus_default(&bus); | |
129 | if (r < 0) | |
130 | fprintf(stderr, "Failed to allocate bus: %s\n", strerror(-r)); | |
131 | … | |
132 | }</programlisting> | |
133 | ||
134 | <para><function>sd_bus_ref()</function>, | |
135 | <function>sd_bus_unref()</function> and | |
136 | <function>sd_bus_unrefp()</function> execute no operation if the | |
137 | passed in bus object is <constant>NULL</constant>.</para> | |
cd6d5e1c ZJS |
138 | </refsect1> |
139 | ||
140 | <refsect1> | |
141 | <title>Return Value</title> | |
142 | ||
143 | <para>On success, <function>sd_bus_new()</function> returns 0 or a | |
144 | positive integer. On failure, it returns a negative errno-style | |
145 | error code.</para> | |
146 | ||
4afd3348 | 147 | <para><function>sd_bus_ref()</function> always returns the argument. |
cd6d5e1c ZJS |
148 | </para> |
149 | ||
4afd3348 | 150 | <para><function>sd_bus_unref()</function> always returns |
cd6d5e1c ZJS |
151 | <constant>NULL</constant>.</para> |
152 | </refsect1> | |
153 | ||
154 | <refsect1> | |
155 | <title>Errors</title> | |
156 | ||
157 | <para>Returned errors may indicate the following problems:</para> | |
158 | ||
159 | <variablelist> | |
160 | <varlistentry> | |
8474b70c | 161 | <term><constant>-ENOMEM</constant></term> |
cd6d5e1c ZJS |
162 | |
163 | <listitem><para>Memory allocation failed.</para></listitem> | |
164 | </varlistentry> | |
165 | </variablelist> | |
166 | </refsect1> | |
167 | ||
168 | <refsect1> | |
169 | <title>Notes</title> | |
170 | ||
171 | <para><function>sd_bus_new()</function> and other functions | |
172 | described here are available as a shared library, which can be | |
173 | compiled and linked to with the | |
5aded369 | 174 | <constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> |
cd6d5e1c ZJS |
175 | file.</para> |
176 | </refsect1> | |
177 | ||
178 | <refsect1> | |
179 | <title>See Also</title> | |
180 | ||
181 | <para> | |
182 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
183 | <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
cd6d5e1c | 184 | <citerefentry><refentrytitle>sd_bus_default_user</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
850df10a LP |
185 | <citerefentry><refentrytitle>sd_bus_default_system</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
186 | <citerefentry><refentrytitle>sd_bus_open_user</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
187 | <citerefentry><refentrytitle>sd_bus_open_system</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
cd6d5e1c ZJS |
188 | </para> |
189 | </refsect1> | |
190 | ||
191 | </refentry> |