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https://github.com/systemd/systemd
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179 lines
8.7 KiB
XML
179 lines
8.7 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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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/4.5/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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<refentry id="sd_bus_message_get_type" xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>sd_bus_message_get_type</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_get_type</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_get_type</refname>
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<refname>sd_bus_message_get_error</refname>
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<refname>sd_bus_message_get_errno</refname>
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<refname>sd_bus_message_get_creds</refname>
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<refname>sd_bus_message_is_signal</refname>
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<refname>sd_bus_message_is_method_call</refname>
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<refname>sd_bus_message_is_method_error</refname>
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<refpurpose>Query bus message addressing/credentials metadata</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_get_type</function></funcdef>
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<paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
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<paramdef>uint8_t *<parameter>type</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>sd_bus_error* <function>sd_bus_message_get_error</function></funcdef>
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<paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_bus_message_get_errno</function></funcdef>
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<paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>sd_bus_creds* <function>sd_bus_message_get_creds</function></funcdef>
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<paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_bus_message_is_signal</function></funcdef>
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<paramdef>sd_bus_message *<parameter>m</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_is_method_call</function></funcdef>
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<paramdef>sd_bus_message *<parameter>m</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_is_method_error</function></funcdef>
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<paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
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<paramdef>const char *<parameter>name</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><function>sd_bus_message_get_type()</function> returns the type of a message in the output
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parameter <parameter>type</parameter>, one of <constant>SD_BUS_MESSAGE_METHOD_CALL</constant>,
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<constant>SD_BUS_MESSAGE_METHOD_RETURN</constant>, <constant>SD_BUS_MESSAGE_METHOD_ERROR</constant>,
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<constant>SD_BUS_MESSAGE_SIGNAL</constant>. This type is either specified as a parameter when the message
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is created using
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<citerefentry><refentrytitle>sd_bus_message_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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or is set automatically when the message is created using
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<citerefentry><refentrytitle>sd_bus_message_new_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_message_new_method_call</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_message_new_method_error</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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and similar functions.</para>
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<para><function>sd_bus_message_get_error()</function> returns the error stored in the message
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<parameter>m</parameter>, if there is any. Otherwise, it returns <constant>NULL</constant>.
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<function>sd_bus_message_get_errno()</function> returns the error stored in the message
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<parameter>m</parameter> as a positive errno-style value, if there is any. Otherwise, it returns zero.
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Errors are mapped to errno values according to the default and any additional registered error mappings.
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See <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry> and
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<citerefentry><refentrytitle>sd_bus_error_add_map</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
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</para>
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<para><function>sd_bus_message_get_creds()</function> returns the message credentials attached to the
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message <parameter>m</parameter>. If no credentials are attached to the message, it returns
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<constant>NULL</constant>. Ownership of the credentials instance is not transferred to the caller and
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hence should not be freed.</para>
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<para><function>sd_bus_message_is_signal()</function> checks if message <parameter>m</parameter> is a
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signal message. If <parameter>interface</parameter> is non-null, it also checks if the message has the
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same interface set. If <parameter>member</parameter> is non-null, it also checks if the message has the
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same member set. Also see
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<citerefentry><refentrytitle>sd_bus_message_new_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
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It returns true when all checks pass.</para>
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<para><function>sd_bus_message_is_method_call()</function> checks if message <parameter>m</parameter>
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is a method call message. If <parameter>interface</parameter> is non-null, it also checks if the message
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has the same interface set. If <parameter>member</parameter> is non-null, it also checks if the message
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has the same member set. Also see
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<citerefentry><refentrytitle>sd_bus_message_new_method_call</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
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It returns true when all checks pass.</para>
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<para><function>sd_bus_message_is_method_error()</function> checks if message <parameter>m</parameter>
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is an error reply message. If <parameter>name</parameter> is non-null, it also checks if the message has
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the same error identifier set. Also see
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<citerefentry><refentrytitle>sd_bus_message_new_method_error</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
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It returns true when all checks pass.</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 (except <function>sd_bus_message_get_error()</function> and
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<function>sd_bus_message_get_creds()</function>) return a non-negative integer. On failure, they return a
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negative errno-style error code. <function>sd_bus_message_get_errno()</function> always returns a
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non-negative integer, even on failure.</para>
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<refsect2>
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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 message parameter <parameter>m</parameter> or an output parameter is
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<constant>NULL</constant>.</para></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>History</title>
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<para><function>sd_bus_message_get_type()</function>,
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<function>sd_bus_message_is_signal()</function>,
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<function>sd_bus_message_is_method_call()</function>, and
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<function>sd_bus_message_is_method_error()</function> were added in version 240.</para>
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<para><function>sd_bus_message_get_error()</function>,
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<function>sd_bus_message_get_errno()</function>, and
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<function>sd_bus_message_get_creds()</function> were added in version 246.</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para><simplelist type="inline">
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<member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>sd_bus_message_new</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>sd_bus_message_set_destination</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>sd_bus_error_add_map</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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</simplelist></para>
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</refsect1>
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</refentry>
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