]>
Commit | Line | Data |
---|---|---|
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> |
cd6d5e1c ZJS |
26 | |
27 | <refpurpose>Create a new bus object and create or destroy references to it</refpurpose> | |
28 | </refnamediv> | |
29 | ||
30 | <refsynopsisdiv> | |
31 | <funcsynopsis> | |
32 | <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> | |
33 | ||
34 | <funcprototype> | |
35 | <funcdef>int <function>sd_bus_new</function></funcdef> | |
8dc385e7 | 36 | <paramdef>sd_bus **<parameter>bus</parameter></paramdef> |
cd6d5e1c ZJS |
37 | </funcprototype> |
38 | ||
39 | <funcprototype> | |
8dc385e7 JE |
40 | <funcdef>sd_bus *<function>sd_bus_ref</function></funcdef> |
41 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> | |
cd6d5e1c ZJS |
42 | </funcprototype> |
43 | ||
44 | <funcprototype> | |
8dc385e7 JE |
45 | <funcdef>sd_bus *<function>sd_bus_unref</function></funcdef> |
46 | <paramdef>sd_bus *<parameter>bus</parameter></paramdef> | |
cd6d5e1c | 47 | </funcprototype> |
4afd3348 LP |
48 | |
49 | <funcprototype> | |
50 | <funcdef>void <function>sd_bus_unrefp</function></funcdef> | |
2c47fff6 | 51 | <paramdef>sd_bus **<parameter>busp</parameter></paramdef> |
4afd3348 | 52 | </funcprototype> |
cd6d5e1c ZJS |
53 | </funcsynopsis> |
54 | </refsynopsisdiv> | |
55 | ||
56 | <refsect1> | |
57 | <title>Description</title> | |
58 | ||
59 | <para><function>sd_bus_new()</function> creates a new bus | |
73e231ab | 60 | object. This object is reference-counted, and will be destroyed |
cd6d5e1c | 61 | when all references are gone. Initially, the caller of this |
db03761e UTL |
62 | function owns the sole reference and the bus object will not be |
63 | connected to any bus. To connect it to a bus, make sure | |
850df10a LP |
64 | to set an address with |
65 | <citerefentry><refentrytitle>sd_bus_set_address</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
66 | or a related call, and then start the connection with | |
67 | <citerefentry><refentrytitle>sd_bus_start</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> | |
68 | ||
7ca41557 | 69 | <para>In most cases, it is a better idea to invoke |
850df10a LP |
70 | <citerefentry><refentrytitle>sd_bus_default_user</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
71 | <citerefentry><refentrytitle>sd_bus_default_system</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
72 | or related calls instead of the more low-level | |
73 | <function>sd_bus_new()</function> and | |
74 | <function>sd_bus_start()</function>. The higher-level calls not | |
75 | only allocate a bus object but also start the connection to a | |
76 | well-known bus in a single function invocation.</para> | |
cd6d5e1c | 77 | |
4afd3348 LP |
78 | <para><function>sd_bus_ref()</function> increases the reference |
79 | counter of <parameter>bus</parameter> by one.</para> | |
cd6d5e1c | 80 | |
4afd3348 LP |
81 | <para><function>sd_bus_unref()</function> decreases the reference |
82 | counter of <parameter>bus</parameter> by one. Once the reference | |
83 | count has dropped to zero, <parameter>bus</parameter> is destroyed | |
84 | and cannot be used anymore, so further calls to | |
85 | <function>sd_bus_ref()</function> or | |
db03761e | 86 | <function>sd_bus_unref()</function> are illegal.</para> |
4afd3348 LP |
87 | |
88 | <para><function>sd_bus_unrefp()</function> is similar to | |
89 | <function>sd_bus_unref()</function> but takes a pointer to a | |
90 | pointer to an <type>sd_bus</type> object. This call is useful in | |
91 | conjunction with GCC's and LLVM's <ulink | |
92 | url="https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up | |
93 | Variable Attribute</ulink>. Note that this function is defined as | |
94 | inline function. Use a declaration like the following, in order to | |
95 | allocate a bus object that is freed automatically as the code | |
96 | block is left:</para> | |
97 | ||
98 | <programlisting>{ | |
787f78b6 ZJS |
99 | __attribute__((cleanup(sd_bus_unrefp)) sd_bus *bus = NULL; |
100 | int r; | |
101 | … | |
102 | r = sd_bus_default(&bus); | |
103 | if (r < 0) | |
104 | fprintf(stderr, "Failed to allocate bus: %s\n", strerror(-r)); | |
105 | … | |
4afd3348 LP |
106 | }</programlisting> |
107 | ||
2c47fff6 ZJS |
108 | <para><function>sd_bus_ref()</function> and <function>sd_bus_unref()</function> |
109 | execute no operation if the passed in bus object address is | |
110 | <constant>NULL</constant>. <function>sd_bus_unrefp()</function> will first | |
111 | dereference its argument, which must not be <constant>NULL</constant>, and will | |
112 | execute no operation if <emphasis>that</emphasis> is <constant>NULL</constant>. | |
113 | </para> | |
cd6d5e1c ZJS |
114 | </refsect1> |
115 | ||
116 | <refsect1> | |
117 | <title>Return Value</title> | |
118 | ||
119 | <para>On success, <function>sd_bus_new()</function> returns 0 or a | |
120 | positive integer. On failure, it returns a negative errno-style | |
121 | error code.</para> | |
122 | ||
4afd3348 | 123 | <para><function>sd_bus_ref()</function> always returns the argument. |
cd6d5e1c ZJS |
124 | </para> |
125 | ||
4afd3348 | 126 | <para><function>sd_bus_unref()</function> always returns |
cd6d5e1c ZJS |
127 | <constant>NULL</constant>.</para> |
128 | </refsect1> | |
129 | ||
130 | <refsect1> | |
131 | <title>Errors</title> | |
132 | ||
133 | <para>Returned errors may indicate the following problems:</para> | |
134 | ||
135 | <variablelist> | |
136 | <varlistentry> | |
8474b70c | 137 | <term><constant>-ENOMEM</constant></term> |
cd6d5e1c ZJS |
138 | |
139 | <listitem><para>Memory allocation failed.</para></listitem> | |
140 | </varlistentry> | |
141 | </variablelist> | |
142 | </refsect1> | |
143 | ||
7d6b2723 | 144 | <xi:include href="libsystemd-pkgconfig.xml" /> |
cd6d5e1c ZJS |
145 | |
146 | <refsect1> | |
147 | <title>See Also</title> | |
148 | ||
149 | <para> | |
150 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
151 | <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
cd6d5e1c | 152 | <citerefentry><refentrytitle>sd_bus_default_user</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
850df10a LP |
153 | <citerefentry><refentrytitle>sd_bus_default_system</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
154 | <citerefentry><refentrytitle>sd_bus_open_user</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
155 | <citerefentry><refentrytitle>sd_bus_open_system</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
cd6d5e1c ZJS |
156 | </para> |
157 | </refsect1> | |
158 | ||
159 | </refentry> |