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<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
This file is part of systemd.
Copyright 2016 Julian Orth
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->
<refentry id="sd_bus_add_match">
<refentryinfo>
<title>sd_bus_add_match</title>
<productname>systemd</productname>
<authorgroup>
<author>
<firstname>Julian</firstname>
<surname>Orth</surname>
<email>ju.orth@gmail.com</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>sd_bus_add_match</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>sd_bus_add_match</refname>
<refpurpose>Add a match rule for message dispatching</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
<funcprototype>
<funcdef>int <function>sd_bus_add_match</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef>
<paramdef>const char *<parameter>match</parameter></paramdef>
<paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef>
<paramdef>void *<parameter>userdata</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>typedef int (*<function>sd_bus_message_handler_t</function>)</funcdef>
<paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
<paramdef>void *<parameter>userdata</parameter></paramdef>
<paramdef>sd_bus_error *<parameter>ret_error</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>
<function>sd_bus_add_match()</function> installs a match rule for incoming messages received on the specified bus
connection object <parameter>bus</parameter>. The syntax of the match rule expression passed in
<parameter>match</parameter> is described in the <ulink
url="https://dbus.freedesktop.org/doc/dbus-specification.html">D-Bus Specification</ulink>. The specified handler
function <parameter>callback</parameter> is called for eaching incoming message matching the specified
expression, the <parameter>userdata</parameter> parameter is passed as-is to the callback function.
</para>
<para>
On success, and if non-<constant>NULL</constant>, the <parameter>slot</parameter> return parameter will be set to
a slot object that may be used as a reference to the installed match, and may be utilized to remove it again at a
later time with
<citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If
specified as <constant>NULL</constant> the lifetime of the match is bound to the lifetime of the bus object itself, and the match
cannot be removed independently.
</para>
<para>
The message <parameter>m</parameter> passed to the callback is only borrowed, that is, the callback should not
call <citerefentry><refentrytitle>sd_bus_message_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> on
it. If the callback wants to hold on to the message beyond the lifetime of the callback, it needs to call
<citerefentry><refentrytitle>sd_bus_message_ref</refentrytitle><manvolnum>3</manvolnum></citerefentry> to create
a new reference.
</para>
<para>
If an error occurs during the callback invocation, the callback should return a negative error number. If it
wants other callbacks that match the same rule to be called, it should return 0. Otherwise it should return a
positive integer.
</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para>
On success, <function>sd_bus_add_match()</function> returns 0 or a positive integer. On failure, it returns a
negative errno-style error code.
</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
|
