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