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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"> |
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4 | |
5 | <!-- | |
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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 |
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11 | --> |
12 | ||
48f69d8f | 13 | <refentry id="sd_bus_new"> |
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14 | |
15 | <refentryinfo> | |
16 | <title>sd_bus_new</title> | |
17 | <productname>systemd</productname> | |
18 | ||
19 | <authorgroup> | |
20 | <author> | |
21 | <contrib>A monkey with a typewriter</contrib> | |
22 | <firstname>Zbigniew</firstname> | |
23 | <surname>Jędrzejewski-Szmek</surname> | |
24 | <email>zbyszek@in.waw.pl</email> | |
25 | </author> | |
26 | </authorgroup> | |
27 | </refentryinfo> | |
28 | ||
29 | <refmeta> | |
30 | <refentrytitle>sd_bus_new</refentrytitle> | |
31 | <manvolnum>3</manvolnum> | |
32 | </refmeta> | |
33 | ||
34 | <refnamediv> | |
35 | <refname>sd_bus_new</refname> | |
36 | <refname>sd_bus_ref</refname> | |
37 | <refname>sd_bus_unref</refname> | |
4afd3348 | 38 | <refname>sd_bus_unrefp</refname> |
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39 | |
40 | <refpurpose>Create a new bus object and create or destroy references to it</refpurpose> | |
41 | </refnamediv> | |
42 | ||
43 | <refsynopsisdiv> | |
44 | <funcsynopsis> | |
45 | <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> | |
46 | ||
47 | <funcprototype> | |
48 | <funcdef>int <function>sd_bus_new</function></funcdef> | |
8dc385e7 | 49 | <paramdef>sd_bus **<parameter>bus</parameter></paramdef> |
cd6d5e1c ZJS |
50 | </funcprototype> |
51 | ||
52 | <funcprototype> | |
8dc385e7 JE |
53 | <funcdef>sd_bus *<function>sd_bus_ref</function></funcdef> |
54 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> | |
cd6d5e1c ZJS |
55 | </funcprototype> |
56 | ||
57 | <funcprototype> | |
8dc385e7 JE |
58 | <funcdef>sd_bus *<function>sd_bus_unref</function></funcdef> |
59 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> | |
cd6d5e1c | 60 | </funcprototype> |
4afd3348 LP |
61 | |
62 | <funcprototype> | |
63 | <funcdef>void <function>sd_bus_unrefp</function></funcdef> | |
64 | <paramdef>sd_bus **<parameter>bus</parameter></paramdef> | |
65 | </funcprototype> | |
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66 | </funcsynopsis> |
67 | </refsynopsisdiv> | |
68 | ||
69 | <refsect1> | |
70 | <title>Description</title> | |
71 | ||
72 | <para><function>sd_bus_new()</function> creates a new bus | |
73e231ab | 73 | object. This object is reference-counted, and will be destroyed |
cd6d5e1c | 74 | when all references are gone. Initially, the caller of this |
db03761e UTL |
75 | function owns the sole reference and the bus object will not be |
76 | connected to any bus. To connect it to a bus, make sure | |
850df10a LP |
77 | to set an address with |
78 | <citerefentry><refentrytitle>sd_bus_set_address</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
79 | or a related call, and then start the connection with | |
80 | <citerefentry><refentrytitle>sd_bus_start</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> | |
81 | ||
7ca41557 | 82 | <para>In most cases, it is a better idea to invoke |
850df10a LP |
83 | <citerefentry><refentrytitle>sd_bus_default_user</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
84 | <citerefentry><refentrytitle>sd_bus_default_system</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
85 | or related calls instead of the more low-level | |
86 | <function>sd_bus_new()</function> and | |
87 | <function>sd_bus_start()</function>. The higher-level calls not | |
88 | only allocate a bus object but also start the connection to a | |
89 | well-known bus in a single function invocation.</para> | |
cd6d5e1c | 90 | |
4afd3348 LP |
91 | <para><function>sd_bus_ref()</function> increases the reference |
92 | counter of <parameter>bus</parameter> by one.</para> | |
cd6d5e1c | 93 | |
4afd3348 LP |
94 | <para><function>sd_bus_unref()</function> decreases the reference |
95 | counter of <parameter>bus</parameter> by one. Once the reference | |
96 | count has dropped to zero, <parameter>bus</parameter> is destroyed | |
97 | and cannot be used anymore, so further calls to | |
98 | <function>sd_bus_ref()</function> or | |
db03761e | 99 | <function>sd_bus_unref()</function> are illegal.</para> |
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100 | |
101 | <para><function>sd_bus_unrefp()</function> is similar to | |
102 | <function>sd_bus_unref()</function> but takes a pointer to a | |
103 | pointer to an <type>sd_bus</type> object. This call is useful in | |
104 | conjunction with GCC's and LLVM's <ulink | |
105 | url="https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up | |
106 | Variable Attribute</ulink>. Note that this function is defined as | |
107 | inline function. Use a declaration like the following, in order to | |
108 | allocate a bus object that is freed automatically as the code | |
109 | block is left:</para> | |
110 | ||
111 | <programlisting>{ | |
112 | __attribute__((cleanup(sd_bus_unrefp)) sd_bus *bus = NULL; | |
113 | int r; | |
114 | … | |
115 | r = sd_bus_default(&bus); | |
116 | if (r < 0) | |
117 | fprintf(stderr, "Failed to allocate bus: %s\n", strerror(-r)); | |
118 | … | |
119 | }</programlisting> | |
120 | ||
121 | <para><function>sd_bus_ref()</function>, | |
122 | <function>sd_bus_unref()</function> and | |
123 | <function>sd_bus_unrefp()</function> execute no operation if the | |
124 | passed in bus object is <constant>NULL</constant>.</para> | |
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125 | </refsect1> |
126 | ||
127 | <refsect1> | |
128 | <title>Return Value</title> | |
129 | ||
130 | <para>On success, <function>sd_bus_new()</function> returns 0 or a | |
131 | positive integer. On failure, it returns a negative errno-style | |
132 | error code.</para> | |
133 | ||
4afd3348 | 134 | <para><function>sd_bus_ref()</function> always returns the argument. |
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135 | </para> |
136 | ||
4afd3348 | 137 | <para><function>sd_bus_unref()</function> always returns |
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138 | <constant>NULL</constant>.</para> |
139 | </refsect1> | |
140 | ||
141 | <refsect1> | |
142 | <title>Errors</title> | |
143 | ||
144 | <para>Returned errors may indicate the following problems:</para> | |
145 | ||
146 | <variablelist> | |
147 | <varlistentry> | |
8474b70c | 148 | <term><constant>-ENOMEM</constant></term> |
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149 | |
150 | <listitem><para>Memory allocation failed.</para></listitem> | |
151 | </varlistentry> | |
152 | </variablelist> | |
153 | </refsect1> | |
154 | ||
155 | <refsect1> | |
156 | <title>Notes</title> | |
157 | ||
158 | <para><function>sd_bus_new()</function> and other functions | |
159 | described here are available as a shared library, which can be | |
160 | compiled and linked to with the | |
5aded369 | 161 | <constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> |
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162 | file.</para> |
163 | </refsect1> | |
164 | ||
165 | <refsect1> | |
166 | <title>See Also</title> | |
167 | ||
168 | <para> | |
169 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
170 | <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
cd6d5e1c | 171 | <citerefentry><refentrytitle>sd_bus_default_user</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
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172 | <citerefentry><refentrytitle>sd_bus_default_system</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
173 | <citerefentry><refentrytitle>sd_bus_open_user</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
174 | <citerefentry><refentrytitle>sd_bus_open_system</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
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175 | </para> |
176 | </refsect1> | |
177 | ||
178 | </refentry> |