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173 lines
7.2 KiB
XML
173 lines
7.2 KiB
XML
<?xml version='1.0'?>
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1+ -->
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<refentry id="sd_bus_message_new_method_call"
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xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>sd_bus_message_new_method_call</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>sd_bus_message_new_method_call</refentrytitle>
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<manvolnum>3</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>sd_bus_message_new_method_call</refname>
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<refname>sd_bus_message_new_method_return</refname>
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<refpurpose>Create a method call message</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
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<funcprototype>
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<funcdef>int <function>sd_bus_message_new_method_call</function></funcdef>
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<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
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<paramdef>sd_bus_message **<parameter>m</parameter></paramdef>
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<paramdef>const char *<parameter>destination</parameter></paramdef>
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<paramdef>const char *<parameter>path</parameter></paramdef>
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<paramdef>const char *<parameter>interface</parameter></paramdef>
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<paramdef>const char *<parameter>member</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_bus_message_new_method_return</function></funcdef>
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<paramdef>sd_bus_message *<parameter>call</parameter></paramdef>
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<paramdef>sd_bus_message **<parameter>m</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para>The <function>sd_bus_message_new_method_call()</function> function creates a new bus
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message object that encapsulates a D-Bus method call, and returns it in the
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<parameter>m</parameter> output parameter. The call will be made on the destination
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<parameter>destination</parameter>, path <parameter>path</parameter>, on the interface
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<parameter>interface</parameter>, member <parameter>member</parameter>.</para>
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<para>Briefly, the <emphasis>destination</emphasis> is a dot-separated name that identifies a
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service connected to the bus. The <emphasis>path</emphasis> is a slash-separated identifier of
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an object within the destination that resembles a file system path. The meaning of this path is
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defined by the destination. The <emphasis>interface</emphasis> is a dot-separated name that
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resembles a Java interface name that identifies a group of methods and signals supported by the
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object identified by path. Methods and signals are collectively called
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<emphasis>members</emphasis> and are identified by a simple name composed of ASCII letters,
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numbers, and underscores. See the <ulink
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url="https://dbus.freedesktop.org/doc/dbus-tutorial.html#concepts">D-Bus Tutorial</ulink> for an
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in-depth explanation.</para>
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<para>The <parameter>destination</parameter> parameter may be <constant>NULL</constant>. The
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<parameter>interface</parameter> parameter may be <constant>NULL</constant>, if the destination
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has only a single member with the given name and there is no ambiguity if the interface name is
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omitted.</para>
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<para>Note that this is a low level interface. See
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<citerefentry><refentrytitle>sd_bus_call_method</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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for a more convenient way of calling D-Bus methods.</para>
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<para>The <function>sd_bus_message_new_method_return()</function> function creates a new bus
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message object that is a reply to the method call <parameter>call</parameter> and returns it in
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the <parameter>m</parameter> output parameter. The <parameter>call</parameter> parameter must be
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a method call message. The sender of <parameter>call</parameter> is used as the destination.
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</para>
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</refsect1>
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<refsect1>
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<title>Return Value</title>
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<para>On success, these functions return a non-negative integer. On failure, they return a
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negative errno-style error code.</para>
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<refsect2 id='errors'>
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<title>Errors</title>
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<para>Returned errors may indicate the following problems:</para>
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<variablelist>
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<varlistentry>
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<term><constant>-EINVAL</constant></term>
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<listitem><para>The output parameter <parameter>m</parameter> is
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<constant>NULL</constant>.</para>
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<para>The <parameter>destination</parameter> parameter is non-null and is not a valid D-Bus
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service name (<literal>org.somewhere.Something</literal>), the <parameter>path</parameter>
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parameter is not a valid D-Bus path (<literal>/an/object/path</literal>), the
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<parameter>interface</parameter> parameter is non-null and is not a valid D-Bus interface
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name (<literal>an.interface.name</literal>), or the <parameter>member</parameter> parameter
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is not a valid D-Bus member (<literal>Name</literal>).</para>
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<para>The <parameter>call</parameter> parameter is not a method call object.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-ENOTCONN</constant></term>
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<listitem><para>The bus parameter <parameter>bus</parameter> is <constant>NULL</constant> or
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the bus is not connected.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-ENOMEM</constant></term>
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<listitem><para>Memory allocation failed.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-EPERM</constant></term>
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<listitem>
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<para>The <parameter>call</parameter> parameter is not sealed.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-EOPNOTSUPP</constant></term>
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<listitem>
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<para>The <parameter>call</parameter> message does not have a cookie.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect2>
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</refsect1>
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<xi:include href="libsystemd-pkgconfig.xml" />
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<refsect1>
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<title>Examples</title>
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<example>
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<title>Make a call to a D-Bus method that takes a single parameter</title>
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<programlisting><xi:include href="print-unit-path.c" parse="text" /></programlisting>
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<para>This defines a minimally useful program that will open a connection to the bus, create a
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message object, send it, wait for the reply, and finally extract and print the answer. It does
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error handling and proper memory management.</para>
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</example>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_call</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_call_method</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_path_encode</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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