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11a1589223
Files which are installed as-is (any .service and other unit files, .conf files, .policy files, etc), are left as is. My assumption is that SPDX identifiers are not yet that well known, so it's better to retain the extended header to avoid any doubt. I also kept any copyright lines. We can probably remove them, but it'd nice to obtain explicit acks from all involved authors before doing that.
183 lines
9.3 KiB
XML
183 lines
9.3 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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-->
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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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<refname>sd_bus_add_match_async</refname>
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<refname>sd_bus_match_signal</refname>
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<refname>sd_bus_match_signal_async</refname>
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<refpurpose>Add a match rule for incoming 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>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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<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>int <function>sd_bus_add_match_async</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>sd_bus_message_handler_t <parameter>install_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>int <function>sd_bus_match_signal</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>sender</parameter></paramdef>
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<paramdef>const char *<parameter>path</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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<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>int <function>sd_bus_match_signal_async</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>sender</parameter></paramdef>
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<paramdef>const char *<parameter>path</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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<paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef>
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<paramdef>sd_bus_message_handler_t <parameter>install_callback</parameter></paramdef>
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<paramdef>void *<parameter>userdata</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_add_match()</function> installs a match rule for 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 expression,
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the <parameter>userdata</parameter> parameter is passed as-is to the callback function. The match is installed
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synchronously when connected to a bus broker, i.e. the call sends a control message requested the match to be added
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to the broker and waits until the broker confirms the match has been installed successfully.</para>
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<para><function>sd_bus_add_match_async()</function> operates very similar to
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<function>sd_bus_match_signal()</function>, however it installs the match asynchronously, in a non-blocking
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fashion: a request is sent to the broker, but the call does not wait for a response. The
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<parameter>install_callback</parameter> function is called when the response is later received, with the response
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message from the broker as parameter. If this function is specified as <constant>NULL</constant> a default
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implementation is used that terminates the bus connection should installing the match fail.</para>
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<para><function>sd_bus_match_signal()</function> is very similar to <function>sd_bus_add_match()</function>, but
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only matches signals, and instead of a match expression accepts four parameters: <parameter>sender</parameter> (the
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service name of the sender), <parameter>path</parameter> (the object path of the emitting object),
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<parameter>interface</parameter> (the interface the signal belongs to), <parameter>member</parameter> (the signal
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name), from which the match string is internally generated. Optionally, these parameters may be specified as
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<constant>NULL</constant> in which case the relevant field of incoming signals is not tested.</para>
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<para><function>sd_bus_match_signal_async()</function> is combines the signal matching logic of
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<function>sd_bus_match_signal()</function> with the asynchronous behaviour of
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<function>sd_bus_add_match_async()</function>.</para>
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<para>On success, and if non-<constant>NULL</constant>, the <parameter>slot</parameter> return parameter will be
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set to a slot object that may be used as a reference to the installed match, and may be utilized to remove it again
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at a later time with
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<citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If specified
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as <constant>NULL</constant> the lifetime of the match is bound to the lifetime of the bus object itself, and the
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match cannot be removed independently.</para>
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<para>The message <parameter>m</parameter> passed to the callback is only borrowed, that is, the callback should
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not call <citerefentry><refentrytitle>sd_bus_message_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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on 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 a
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new reference.</para>
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<para>If an error occurs during the callback invocation, the callback should return a negative error number
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(optionally, a more precise error may be returned in <parameter>ret_error</parameter>, as well). If it wants other
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callbacks that match the same rule to be called, it should return 0. Otherwise it should return a positive integer.
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</para>
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<para>If the <parameter>bus</parameter> refers to a direct connection (i.e. not a bus connection, as set with
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<citerefentry><refentrytitle>sd_bus_set_bus_client</refentrytitle><manvolnum>3</manvolnum></citerefentry>) the
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match is only installed on the client side, and the synchronous and asynchronous functions operate the same.</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> and the other calls return 0 or a positive integer. On
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failure, they return a 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>Notes</title>
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<para><function>sd_bus_add_match()</function> and the other functions described here are available as a shared
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library, which can be compiled and linked to with the <constant>libsystemd</constant> <citerefentry
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project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> file.</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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<citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_message_ref</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_set_bus_client</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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