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<?xml version='1.0'?> <!--*-nxml-*-->
<!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_get_type" xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>sd_bus_message_get_type</title>
<productname>systemd</productname>
</refentryinfo>
<refmeta>
<refentrytitle>sd_bus_message_get_type</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>sd_bus_message_get_type</refname>
<refname>sd_bus_message_is_signal</refname>
<refname>sd_bus_message_is_method_call</refname>
<refname>sd_bus_message_is_method_error</refname>
<refpurpose>Query bus message addressing metadata</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
<funcprototype>
<funcdef>int <function>sd_bus_message_get_type</function></funcdef>
<paramdef>sd_bus_message *<parameter>message</parameter></paramdef>
<paramdef>uint8_t *<parameter>type</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_bus_message_is_signal</function></funcdef>
<paramdef>sd_bus_message *<parameter>message</parameter></paramdef>
<paramdef>const char *<parameter>interface</parameter></paramdef>
<paramdef>const char *<parameter>member</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_bus_message_is_method_call</function></funcdef>
<paramdef>sd_bus_message *<parameter>message</parameter></paramdef>
<paramdef>const char *<parameter>interface</parameter></paramdef>
<paramdef>const char *<parameter>member</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_bus_message_is_method_error</function></funcdef>
<paramdef>sd_bus_message *<parameter>message</parameter></paramdef>
<paramdef>const char *<parameter>name</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><function>sd_bus_message_get_type()</function> returns the type of a message in the output
parameter <parameter>type</parameter>, one of <constant>SD_BUS_MESSAGE_METHOD_CALL</constant>,
<constant>SD_BUS_MESSAGE_METHOD_RETURN</constant>,
<constant>SD_BUS_MESSAGE_METHOD_ERROR</constant>, <constant>SD_BUS_MESSAGE_SIGNAL</constant>.
This type is either specified as a parameter when the message is created using
<citerefentry><refentrytitle>sd_bus_set_message_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
or is set automatically when the message is created using
<citerefentry><refentrytitle>sd_bus_set_message_new_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_set_message_new_method_call</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_set_message_new_method_error</refentrytitle><manvolnum>3</manvolnum></citerefentry>
and similar functions.
</para>
<para><function>sd_bus_message_is_signal()</function> checks if message <parameter>m</parameter>
is a signal message. If <parameter>interface</parameter> is non-null, it also checks if the
message has the same interface set. If <parameter>member</parameter> is non-null, it also checks
if the message has the same member set. Also see
<citerefentry><refentrytitle>sd_bus_set_message_new_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>. It returns true when all checks pass.</para>
<para><function>sd_bus_message_is_method_call()</function> checks if message <parameter>m</parameter>
is a method call message. If <parameter>interface</parameter> is non-null, it also checks if the
message has the same interface set. If <parameter>member</parameter> is non-null, it also checks
if the message has the same member set. Also see
<citerefentry><refentrytitle>sd_bus_set_message_new_method_call</refentrytitle><manvolnum>3</manvolnum></citerefentry>. It returns true when all checks pass.</para>
<para><function>sd_bus_message_is_method_error()</function> checks if message <parameter>m</parameter>
is an error reply message. If <parameter>name</parameter> is non-null, it also checks if the
message has the same error identifier set. Also see
<citerefentry><refentrytitle>sd_bus_set_message_new_method_error</refentrytitle><manvolnum>3</manvolnum></citerefentry>. It returns true when all checks pass.</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para>On success, those functions return 0 or a positive
integer. On failure, it returns a negative errno-style error code.</para>
</refsect1>
<refsect1>
<title>Errors</title>
<para>Returned errors may indicate the following problems:</para>
<variablelist>
<varlistentry>
<term><constant>-EINVAL</constant></term>
<listitem><para>The <parameter>message</parameter> parameter or the output parameter are
<constant>NULL</constant>.</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<xi:include href="libsystemd-pkgconfig.xml" />
<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_message_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_message_set_destination</refentrytitle><manvolnum>3</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
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