2 <!DOCTYPE refentry PUBLIC
"-//OASIS//DTD DocBook XML V4.5//EN"
3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
4 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
6 <refentry id=
"sd_bus_call"
7 xmlns:
xi=
"http://www.w3.org/2001/XInclude">
10 <title>sd_bus_call
</title>
11 <productname>systemd
</productname>
15 <refentrytitle>sd_bus_call
</refentrytitle>
16 <manvolnum>3</manvolnum>
20 <refname>sd_bus_call
</refname>
21 <refname>sd_bus_call_async
</refname>
23 <refpurpose>Invoke a D-Bus method call
</refpurpose>
28 <funcsynopsisinfo>#include
<systemd/sd-bus.h
></funcsynopsisinfo>
31 <funcdef>int
<function>sd_bus_call
</function></funcdef>
32 <paramdef>sd_bus *
<parameter>bus
</parameter></paramdef>
33 <paramdef>sd_bus_message *
<parameter>m
</parameter></paramdef>
34 <paramdef>uint64_t
<parameter>usec
</parameter></paramdef>
35 <paramdef>sd_bus_error *
<parameter>ret_error
</parameter></paramdef>
36 <paramdef>sd_bus_message **
<parameter>reply
</parameter></paramdef>
40 <funcdef>int
<function>sd_bus_call_async
</function></funcdef>
41 <paramdef>sd_bus *
<parameter>bus
</parameter></paramdef>
42 <paramdef>sd_bus_slot **
<parameter>slot
</parameter></paramdef>
43 <paramdef>sd_bus_message *
<parameter>m
</parameter></paramdef>
44 <paramdef>sd_bus_message_handler_t
<parameter>callback
</parameter></paramdef>
45 <paramdef>void *
<parameter>userdata
</parameter></paramdef>
46 <paramdef>uint64_t
<parameter>usec
</parameter></paramdef>
52 <title>Description
</title>
54 <para><function>sd_bus_call()
</function> takes a complete bus message object and calls the
55 corresponding D-Bus method. On success, the response is stored in
<parameter>reply
</parameter>.
56 <parameter>usec
</parameter> indicates the timeout in microseconds. If
57 <parameter>ret_error
</parameter> is not
<constant>NULL
</constant> and
58 <function>sd_bus_call()
</function> fails (either because of an internal error or because it
59 received a D-Bus error reply),
<parameter>ret_error
</parameter> is initialized to an instance of
60 <structname>sd_bus_error
</structname> describing the error.
</para>
62 <para><function>sd_bus_call_async()
</function> is like
<function>sd_bus_call()
</function> but
63 works asynchronously. The
<parameter>callback
</parameter> indicates the function to call when
64 the response arrives. The
<parameter>userdata
</parameter> pointer will be passed to the callback
65 function, and may be chosen freely by the caller. If
<parameter>slot
</parameter> is not
66 <constant>NULL
</constant> and
<function>sd_bus_call_async()
</function> succeeds,
67 <parameter>slot
</parameter> is set to a slot object which can be used to cancel the method call
69 <citerefentry><refentrytitle>sd_bus_slot_unref
</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
70 If
<parameter>slot
</parameter> is
<constant>NULL
</constant>, the lifetime of the method call is
71 bound to the lifetime of the bus object itself, and it cannot be cancelled independently. See
72 <citerefentry><refentrytitle>sd_bus_slot_set_floating
</refentrytitle><manvolnum>3</manvolnum></citerefentry>
73 for details.
<parameter>callback
</parameter> is called when a reply arrives with the reply,
74 <parameter>userdata
</parameter> and an
<structname>sd_bus_error
</structname> output
75 parameter as its arguments. Unlike
<function>sd_bus_call()
</function>, the
76 <structname>sd_bus_error
</structname> output parameter passed to the callback will be empty. To
77 determine whether the method call succeeded, use
78 <citerefentry><refentrytitle>sd_bus_message_is_method_error
</refentrytitle><manvolnum>3</manvolnum></citerefentry>
79 on the reply message passed to the callback instead. If the callback returns zero and the
80 <structname>sd_bus_error
</structname> output parameter is still empty when the callback
81 inishes, other handlers registered with functions such as
82 <citerefentry><refentrytitle>sd_bus_add_filter
</refentrytitle><manvolnum>3</manvolnum></citerefentry> or
83 <citerefentry><refentrytitle>sd_bus_add_match
</refentrytitle><manvolnum>3</manvolnum></citerefentry>
84 are given a chance to process the message. If the callback returns a non-zero value or the
85 <structname>sd_bus_error
</structname> output parameter is not empty when the callback finishes,
86 no further processing of the message is done. Generally, you want to return zero from the
87 callback to give other registered handlers a chance to process the reply as well.
</para>
89 <para>If
<parameter>usec
</parameter> is zero, the default D-Bus method call timeout is used. See
90 <citerefentry><refentrytitle>sd_bus_get_method_call_timeout
</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
96 <title>Return Value
</title>
98 <para>On success, these functions return a non-negative integer. On failure, they return a
99 negative errno-style error code.
</para>
101 <refsect2 id='errors'
>
102 <title>Errors
</title>
104 <para>Returned errors may indicate the following problems:
</para>
108 <term><constant>-EINVAL
</constant></term>
110 <listitem><para>The input parameter
<parameter>m
</parameter> is
<constant>NULL
</constant>.
113 <listitem><para>The input parameter
<parameter>m
</parameter> is not a D-Bus method call.
114 To create a new D-Bus method call, use
115 <citerefentry><refentrytitle>sd_bus_message_new_method_call
</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
118 <listitem><para>The input parameter
<parameter>m
</parameter> has the
119 <constant>BUS_MESSAGE_NO_REPLY_EXPECTED
</constant> flag set.
</para></listitem>
121 <listitem><para>The input parameter
<parameter>error
</parameter> is
122 non-
<constant>NULL
</constant> but was not set to
<constant>SD_BUS_ERROR_NULL
</constant>.
127 <term><constant>-ECHILD
</constant></term>
129 <listitem><para>The bus connection was allocated in a parent process and is being reused
130 in a child process after
<function>fork()
</function>.
</para></listitem>
134 <term><constant>-ENOTCONN
</constant></term>
136 <listitem><para>The input parameter
<parameter>bus
</parameter> is
137 <constant>NULL
</constant> or the bus is not connected.
</para></listitem>
141 <term><constant>-ECONNRESET
</constant></term>
143 <listitem><para>The bus connection was closed while waiting for the response.
148 <term><constant>-ETIMEDOUT
</constant></term>
150 <listitem><para>A response was not received within the given timeout.
</para></listitem>
154 <term><constant>-ELOOP
</constant></term>
156 <listitem><para>The message
<parameter>m
</parameter> is addressed to its own client.
161 <term><constant>-ENOMEM
</constant></term>
163 <listitem><para>Memory allocation failed.
</para></listitem>
169 <xi:include href=
"libsystemd-pkgconfig.xml" />
172 <title>See Also
</title>
175 <citerefentry><refentrytitle>systemd
</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
176 <citerefentry><refentrytitle>sd-bus
</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
177 <citerefentry><refentrytitle>sd_bus_call_method
</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
178 <citerefentry><refentrytitle>sd_bus_call_method_async
</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
179 <citerefentry><refentrytitle>sd_bus_message_new_method_call
</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
180 <citerefentry><refentrytitle>sd_bus_message_append
</refentrytitle><manvolnum>3</manvolnum></citerefentry>