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<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
<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_get_error</refname>
<refname>sd_bus_message_get_errno</refname>
<refname>sd_bus_message_get_creds</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/credentials 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>m</parameter></paramdef>
<paramdef>uint8_t *<parameter>type</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>sd_bus_error* <function>sd_bus_message_get_error</function></funcdef>
<paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_bus_message_get_errno</function></funcdef>
<paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>sd_bus_creds* <function>sd_bus_message_get_creds</function></funcdef>
<paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_bus_message_is_signal</function></funcdef>
<paramdef>sd_bus_message *<parameter>m</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>m</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>m</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_message_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
or is set automatically when the message is created using
<citerefentry><refentrytitle>sd_bus_message_new_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_message_new_method_call</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_message_new_method_error</refentrytitle><manvolnum>3</manvolnum></citerefentry>
and similar functions.</para>
<para><function>sd_bus_message_get_error()</function> returns the error stored in the message
<parameter>m</parameter>, if there is any. Otherwise, it returns <constant>NULL</constant>.
<function>sd_bus_message_get_errno()</function> returns the error stored in the message
<parameter>m</parameter> as a positive errno-style value, if there is any. Otherwise, it returns zero.
Errors are mapped to errno values according to the default and any additional registered error mappings.
See <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry> and
<citerefentry><refentrytitle>sd_bus_error_add_map</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
</para>
<para><function>sd_bus_message_get_creds()</function> returns the message credentials attached to the
message <parameter>m</parameter>. If no credentials are attached to the message, it returns
<constant>NULL</constant>. Ownership of the credentials instance is not transferred to the caller and
hence should not be freed.</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_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_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_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, these functions (except <function>sd_bus_message_get_error()</function> and
<function>sd_bus_message_get_creds()</function>) return a non-negative integer. On failure, they return a
negative errno-style error code. <function>sd_bus_message_get_errno()</function> always returns a
non-negative integer, even on failure.</para>
<refsect2>
<title>Errors</title>
<para>Returned errors may indicate the following problems:</para>
<variablelist>
<varlistentry>
<term><constant>-EINVAL</constant></term>
<listitem><para>The message parameter <parameter>m</parameter> or an output parameter is
<constant>NULL</constant>.</para></listitem>
</varlistentry>
</variablelist>
</refsect2>
</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>,
<citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_error_add_map</refentrytitle><manvolnum>3</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
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