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514094f9 | 1 | <?xml version='1.0'?> |
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 | 6 | SPDX-License-Identifier: LGPL-2.1+ |
cd6d5e1c ZJS |
7 | --> |
8 | ||
7d6b2723 | 9 | <refentry id="sd_bus_new" xmlns:xi="http://www.w3.org/2001/XInclude"> |
cd6d5e1c ZJS |
10 | |
11 | <refentryinfo> | |
12 | <title>sd_bus_new</title> | |
13 | <productname>systemd</productname> | |
cd6d5e1c ZJS |
14 | </refentryinfo> |
15 | ||
16 | <refmeta> | |
17 | <refentrytitle>sd_bus_new</refentrytitle> | |
18 | <manvolnum>3</manvolnum> | |
19 | </refmeta> | |
20 | ||
21 | <refnamediv> | |
22 | <refname>sd_bus_new</refname> | |
23 | <refname>sd_bus_ref</refname> | |
24 | <refname>sd_bus_unref</refname> | |
4afd3348 | 25 | <refname>sd_bus_unrefp</refname> |
eda0d9a1 LP |
26 | <refname>sd_bus_flush_close_unref</refname> |
27 | <refname>sd_bus_flush_close_unrefp</refname> | |
cd6d5e1c ZJS |
28 | |
29 | <refpurpose>Create a new bus object and create or destroy references to it</refpurpose> | |
30 | </refnamediv> | |
31 | ||
32 | <refsynopsisdiv> | |
33 | <funcsynopsis> | |
34 | <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> | |
35 | ||
36 | <funcprototype> | |
37 | <funcdef>int <function>sd_bus_new</function></funcdef> | |
8dc385e7 | 38 | <paramdef>sd_bus **<parameter>bus</parameter></paramdef> |
cd6d5e1c ZJS |
39 | </funcprototype> |
40 | ||
41 | <funcprototype> | |
8dc385e7 JE |
42 | <funcdef>sd_bus *<function>sd_bus_ref</function></funcdef> |
43 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> | |
cd6d5e1c ZJS |
44 | </funcprototype> |
45 | ||
46 | <funcprototype> | |
8dc385e7 JE |
47 | <funcdef>sd_bus *<function>sd_bus_unref</function></funcdef> |
48 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> | |
cd6d5e1c | 49 | </funcprototype> |
4afd3348 LP |
50 | |
51 | <funcprototype> | |
52 | <funcdef>void <function>sd_bus_unrefp</function></funcdef> | |
2c47fff6 | 53 | <paramdef>sd_bus **<parameter>busp</parameter></paramdef> |
4afd3348 | 54 | </funcprototype> |
eda0d9a1 LP |
55 | |
56 | <funcprototype> | |
57 | <funcdef>sd_bus *<function>sd_bus_flush_close_unref</function></funcdef> | |
58 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> | |
59 | </funcprototype> | |
60 | ||
61 | <funcprototype> | |
62 | <funcdef>void <function>sd_bus_flush_close_unrefp</function></funcdef> | |
63 | <paramdef>sd_bus **<parameter>busp</parameter></paramdef> | |
64 | </funcprototype> | |
cd6d5e1c ZJS |
65 | </funcsynopsis> |
66 | </refsynopsisdiv> | |
67 | ||
68 | <refsect1> | |
69 | <title>Description</title> | |
70 | ||
71 | <para><function>sd_bus_new()</function> creates a new bus | |
73e231ab | 72 | object. This object is reference-counted, and will be destroyed |
cd6d5e1c | 73 | when all references are gone. Initially, the caller of this |
db03761e UTL |
74 | function owns the sole reference and the bus object will not be |
75 | connected to any bus. To connect it to a bus, make sure | |
850df10a LP |
76 | to set an address with |
77 | <citerefentry><refentrytitle>sd_bus_set_address</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
78 | or a related call, and then start the connection with | |
79 | <citerefentry><refentrytitle>sd_bus_start</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> | |
80 | ||
7ca41557 | 81 | <para>In most cases, it is a better idea to invoke |
850df10a LP |
82 | <citerefentry><refentrytitle>sd_bus_default_user</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
83 | <citerefentry><refentrytitle>sd_bus_default_system</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
84 | or related calls instead of the more low-level | |
85 | <function>sd_bus_new()</function> and | |
86 | <function>sd_bus_start()</function>. The higher-level calls not | |
87 | only allocate a bus object but also start the connection to a | |
88 | well-known bus in a single function invocation.</para> | |
cd6d5e1c | 89 | |
4afd3348 LP |
90 | <para><function>sd_bus_ref()</function> increases the reference |
91 | counter of <parameter>bus</parameter> by one.</para> | |
cd6d5e1c | 92 | |
4afd3348 LP |
93 | <para><function>sd_bus_unref()</function> decreases the reference |
94 | counter of <parameter>bus</parameter> by one. Once the reference | |
95 | count has dropped to zero, <parameter>bus</parameter> is destroyed | |
96 | and cannot be used anymore, so further calls to | |
97 | <function>sd_bus_ref()</function> or | |
db03761e | 98 | <function>sd_bus_unref()</function> are illegal.</para> |
4afd3348 LP |
99 | |
100 | <para><function>sd_bus_unrefp()</function> is similar to | |
101 | <function>sd_bus_unref()</function> but takes a pointer to a | |
102 | pointer to an <type>sd_bus</type> object. This call is useful in | |
103 | conjunction with GCC's and LLVM's <ulink | |
104 | url="https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up | |
105 | Variable Attribute</ulink>. Note that this function is defined as | |
106 | inline function. Use a declaration like the following, in order to | |
107 | allocate a bus object that is freed automatically as the code | |
108 | block is left:</para> | |
109 | ||
110 | <programlisting>{ | |
787f78b6 ZJS |
111 | __attribute__((cleanup(sd_bus_unrefp)) sd_bus *bus = NULL; |
112 | int r; | |
113 | … | |
114 | r = sd_bus_default(&bus); | |
115 | if (r < 0) | |
116 | fprintf(stderr, "Failed to allocate bus: %s\n", strerror(-r)); | |
117 | … | |
4afd3348 LP |
118 | }</programlisting> |
119 | ||
2c47fff6 ZJS |
120 | <para><function>sd_bus_ref()</function> and <function>sd_bus_unref()</function> |
121 | execute no operation if the passed in bus object address is | |
122 | <constant>NULL</constant>. <function>sd_bus_unrefp()</function> will first | |
123 | dereference its argument, which must not be <constant>NULL</constant>, and will | |
124 | execute no operation if <emphasis>that</emphasis> is <constant>NULL</constant>. | |
125 | </para> | |
eda0d9a1 LP |
126 | |
127 | <para><function>sd_bus_flush_close_unref()</function> is similar to <function>sd_bus_unref()</function>, but first | |
128 | executes <citerefentry><refentrytitle>sd_bus_flush</refentrytitle><manvolnum>3</manvolnum></citerefentry> as well | |
129 | as <citerefentry><refentrytitle>sd_bus_close</refentrytitle><manvolnum>3</manvolnum></citerefentry>, ensuring that | |
130 | any pending messages are properly flushed out before the reference to the connection is dropped and possibly the | |
131 | object freed. This call is particularly useful immediately before exiting from a program as it ensures that any | |
132 | pending outgoing messages are written out, and unprocessed but queued incoming messages released before the | |
133 | connection is terminated and released.</para> | |
134 | ||
135 | <para><function>sd_bus_flush_close_unrefp()</function> is similar to | |
136 | <function>sd_bus_flush_close_unref()</function>, but may be used in GCC's and LLVM's Clean-up Variable Attribute, | |
137 | see above.</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 | ||
eda0d9a1 | 150 | <para><function>sd_bus_unref()</function> and <function>sd_bus_flush_close_unref()</function> always return |
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 | ||
7d6b2723 | 168 | <xi:include href="libsystemd-pkgconfig.xml" /> |
cd6d5e1c ZJS |
169 | |
170 | <refsect1> | |
171 | <title>See Also</title> | |
172 | ||
173 | <para> | |
174 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
175 | <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
cd6d5e1c | 176 | <citerefentry><refentrytitle>sd_bus_default_user</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
850df10a LP |
177 | <citerefentry><refentrytitle>sd_bus_default_system</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
178 | <citerefentry><refentrytitle>sd_bus_open_user</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
eda0d9a1 LP |
179 | <citerefentry><refentrytitle>sd_bus_open_system</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
180 | <citerefentry><refentrytitle>sd_bus_close</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
cd6d5e1c ZJS |
181 | </para> |
182 | </refsect1> | |
183 | ||
184 | </refentry> |