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
|
<?xml version='1.0'?>
<!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_message_new_method_call"
xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>sd_bus_message_new_method_call</title>
<productname>systemd</productname>
</refentryinfo>
<refmeta>
<refentrytitle>sd_bus_message_new_method_call</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>sd_bus_message_new_method_call</refname>
<refname>sd_bus_message_new_method_return</refname>
<refpurpose>Create a method call message</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
<funcprototype>
<funcdef>int sd_bus_message_new_method_call</funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>sd_bus_message **<parameter>m</parameter></paramdef>
<paramdef>const char *<parameter>destination</parameter></paramdef>
<paramdef>const char *<parameter>path</parameter></paramdef>
<paramdef>const char *<parameter>interface</parameter></paramdef>
<paramdef>const char *<parameter>member</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int sd_bus_message_new_method_return</funcdef>
<paramdef>sd_bus_message *<parameter>call</parameter></paramdef>
<paramdef>sd_bus_message **<parameter>m</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>The <function>sd_bus_message_new_method_call()</function> function creates a new bus
message object that encapsulates a D-Bus method call, and returns it in the
<parameter>m</parameter> output parameter. The call will be made on the destination
<parameter>destination</parameter>, path <parameter>path</parameter>, on the interface
<parameter>interface</parameter>, member <parameter>member</parameter>.</para>
<para>Briefly, the <emphasis>destination</emphasis> is a dot-separated name that identifies a
service connected to the bus. The <emphasis>path</emphasis> is a slash-separated identifier of
an object within the destination that resembles a file system path. The meaning of this path is
defined by the destination. The <emphasis>interface</emphasis> is a dot-separated name that
resembles a Java interface name that identifies a group of methods and signals supported by the
object identified by path. Methods and signals are collectively called
<emphasis>members</emphasis> and are identified by a simple name composed of ASCII letters,
numbers, and underscores. See the <ulink
url="https://dbus.freedesktop.org/doc/dbus-tutorial.html#concepts">D-Bus Tutorial</ulink> for an
in-depth explanation.</para>
<para>The <parameter>destination</parameter> parameter may be <constant>NULL</constant>. The
<parameter>interface</parameter> parameter may be <constant>NULL</constant>, if the destination
has only a single member with the given name and there is no ambiguity if the interface name is
omitted.</para>
<para>The <function>sd_bus_message_new_method_call()</function> function creates a new bus
message object that is a reply to the method call <parameter>call</parameter> and returns it in
the <parameter>m</parameter> output parameter. The <parameter>call</parameter> parameter must be
a method call message. The sender of <parameter>call</parameter> is used as the destination.
</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para>This function returns 0 if the message object was successfully created, and a negative
errno-style error code otherwise.</para>
</refsect1>
<refsect1 id='errors'>
<title>Errors</title>
<para>Returned errors may indicate the following problems:</para>
<variablelist>
<varlistentry>
<term><constant>-EINVAL</constant></term>
<listitem><para>The output parameter <parameter>m</parameter> is
<constant>NULL</constant>.</para>
<para>The <parameter>destination</parameter> parameter is non-null and is not a valid D-Bus
service name (<literal>org.somewhere.Something</literal>), the <parameter>path</parameter>
parameter is not a valid D-Bus path (<literal>/an/object/path</literal>), the
<parameter>interface</parameter> parameter is non-null and is not a valid D-Bus interface
name (<literal>an.interface.name</literal>), or the <parameter>member</parameter> parameter
is not a valid D-Bus member (<literal>Name</literal>).</para>
<para>The <parameter>call</parameter> parameter is not a method call object.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>-ENOTCONN</constant></term>
<listitem><para>The bus parameter <parameter>bus</parameter> is <constant>NULL</constant> or
the bus is not connected.</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>-ENOMEM</constant></term>
<listitem><para>Memory allocation failed.</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>-EPERM</constant></term>
<listitem>
<para>The <parameter>call</parameter> parameter is not sealed.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>-EOPNOTSUPP</constant></term>
<listitem>
<para>The <parameter>call</parameter> message does not have a cookie.</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<xi:include href="libsystemd-pkgconfig.xml" />
<refsect1>
<title>Examples</title>
<example>
<title>Make a call to a D-Bus method that takes a single parameter</title>
<programlisting><xi:include href="print-unit-path.c" parse="text" /></programlisting>
<para>This defines a minimally useful program that will open a connection to the bus, create a
message object, send it, wait for the reply, and finally extract and print the answer. It does
error handling and proper memory management.</para>
</example>
</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_path_encode</refentrytitle><manvolnum>3</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
|
GitWeb