1<?xml version='1.0'?> 2<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" 3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> 4 5<!-- 6 SPDX-License-Identifier: LGPL-2.1-or-later 7 8 Copyright © 2016 Julian Orth 9--> 10 11<refentry id="sd_bus_add_match" xmlns:xi="http://www.w3.org/2001/XInclude"> 12 13 <refentryinfo> 14 <title>sd_bus_add_match</title> 15 <productname>systemd</productname> 16 </refentryinfo> 17 18 <refmeta> 19 <refentrytitle>sd_bus_add_match</refentrytitle> 20 <manvolnum>3</manvolnum> 21 </refmeta> 22 23 <refnamediv> 24 <refname>sd_bus_add_match</refname> 25 <refname>sd_bus_add_match_async</refname> 26 <refname>sd_bus_match_signal</refname> 27 <refname>sd_bus_match_signal_async</refname> 28 29 <refpurpose>Add a match rule for incoming message dispatching</refpurpose> 30 </refnamediv> 31 32 <refsynopsisdiv> 33 <funcsynopsis> 34 <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> 35 36 <funcprototype id="sd_bus_message_handler_t"> 37 <funcdef>typedef int (*<function>sd_bus_message_handler_t</function>)</funcdef> 38 <paramdef>sd_bus_message *<parameter>m</parameter></paramdef> 39 <paramdef>void *<parameter>userdata</parameter></paramdef> 40 <paramdef>sd_bus_error *<parameter>ret_error</parameter></paramdef> 41 </funcprototype> 42 43 <funcprototype> 44 <funcdef>int <function>sd_bus_add_match</function></funcdef> 45 <paramdef>sd_bus *<parameter>bus</parameter></paramdef> 46 <paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef> 47 <paramdef>const char *<parameter>match</parameter></paramdef> 48 <paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef> 49 <paramdef>void *<parameter>userdata</parameter></paramdef> 50 </funcprototype> 51 52 <funcprototype> 53 <funcdef>int <function>sd_bus_add_match_async</function></funcdef> 54 <paramdef>sd_bus *<parameter>bus</parameter></paramdef> 55 <paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef> 56 <paramdef>const char *<parameter>match</parameter></paramdef> 57 <paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef> 58 <paramdef>sd_bus_message_handler_t <parameter>install_callback</parameter></paramdef> 59 <paramdef>void *<parameter>userdata</parameter></paramdef> 60 </funcprototype> 61 62 <funcprototype> 63 <funcdef>int <function>sd_bus_match_signal</function></funcdef> 64 <paramdef>sd_bus *<parameter>bus</parameter></paramdef> 65 <paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef> 66 <paramdef>const char *<parameter>sender</parameter></paramdef> 67 <paramdef>const char *<parameter>path</parameter></paramdef> 68 <paramdef>const char *<parameter>interface</parameter></paramdef> 69 <paramdef>const char *<parameter>member</parameter></paramdef> 70 <paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef> 71 <paramdef>void *<parameter>userdata</parameter></paramdef> 72 </funcprototype> 73 74 <funcprototype> 75 <funcdef>int <function>sd_bus_match_signal_async</function></funcdef> 76 <paramdef>sd_bus *<parameter>bus</parameter></paramdef> 77 <paramdef>sd_bus_slot **<parameter>slot</parameter></paramdef> 78 <paramdef>const char *<parameter>sender</parameter></paramdef> 79 <paramdef>const char *<parameter>path</parameter></paramdef> 80 <paramdef>const char *<parameter>interface</parameter></paramdef> 81 <paramdef>const char *<parameter>member</parameter></paramdef> 82 <paramdef>sd_bus_message_handler_t <parameter>callback</parameter></paramdef> 83 <paramdef>sd_bus_message_handler_t <parameter>install_callback</parameter></paramdef> 84 <paramdef>void *<parameter>userdata</parameter></paramdef> 85 </funcprototype> 86 87 </funcsynopsis> 88 </refsynopsisdiv> 89 90 <refsect1> 91 <title>Description</title> 92 93 <para><function>sd_bus_add_match()</function> installs a match rule for messages received on the specified bus 94 connection object <parameter>bus</parameter>. The syntax of the match rule expression passed in 95 <parameter>match</parameter> is described in the <ulink 96 url="https://dbus.freedesktop.org/doc/dbus-specification.html">D-Bus Specification</ulink>. The specified handler 97 function <parameter>callback</parameter> is called for each incoming message matching the specified expression, 98 the <parameter>userdata</parameter> parameter is passed as-is to the callback function. The match is installed 99 synchronously when connected to a bus broker, i.e. the call sends a control message requested the match to be added 100 to the broker and waits until the broker confirms the match has been installed successfully.</para> 101 102 <para><function>sd_bus_add_match_async()</function> operates very similar to 103 <function>sd_bus_add_match()</function>, however it installs the match asynchronously, in a non-blocking 104 fashion: a request is sent to the broker, but the call does not wait for a response. The 105 <parameter>install_callback</parameter> function is called when the response is later received, with the response 106 message from the broker as parameter. If this function is specified as <constant>NULL</constant> a default 107 implementation is used that terminates the bus connection should installing the match fail.</para> 108 109 <para><function>sd_bus_match_signal()</function> is very similar to <function>sd_bus_add_match()</function>, but 110 only matches signals, and instead of a match expression accepts four parameters: <parameter>sender</parameter> (the 111 service name of the sender), <parameter>path</parameter> (the object path of the emitting object), 112 <parameter>interface</parameter> (the interface the signal belongs to), <parameter>member</parameter> (the signal 113 name), from which the match string is internally generated. Optionally, these parameters may be specified as 114 <constant>NULL</constant> in which case the relevant field of incoming signals is not tested.</para> 115 116 <para><function>sd_bus_match_signal_async()</function> combines the signal matching logic of 117 <function>sd_bus_match_signal()</function> with the asynchronous behaviour of 118 <function>sd_bus_add_match_async()</function>.</para> 119 120 <para>On success, and if non-<constant>NULL</constant>, the <parameter>slot</parameter> return parameter will be 121 set to a slot object that may be used as a reference to the installed match, and may be utilized to remove it again 122 at a later time with 123 <citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If specified 124 as <constant>NULL</constant> the lifetime of the match is bound to the lifetime of the bus object itself, and the 125 match is generally not removed independently. See 126 <citerefentry><refentrytitle>sd_bus_slot_set_floating</refentrytitle><manvolnum>3</manvolnum></citerefentry> for 127 details.</para> 128 129 <para>The message <parameter>m</parameter> passed to the callback is only borrowed, that is, the callback should 130 not call <citerefentry><refentrytitle>sd_bus_message_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> 131 on it. If the callback wants to hold on to the message beyond the lifetime of the callback, it needs to call 132 <citerefentry><refentrytitle>sd_bus_message_ref</refentrytitle><manvolnum>3</manvolnum></citerefentry> to create a 133 new reference.</para> 134 135 <para>If an error occurs during the callback invocation, the callback should return a negative error number 136 (optionally, a more precise error may be returned in <parameter>ret_error</parameter>, as well). If it wants other 137 callbacks that match the same rule to be called, it should return 0. Otherwise it should return a positive integer. 138 </para> 139 140 <para>If the <parameter>bus</parameter> refers to a direct connection (i.e. not a bus connection, as set with 141 <citerefentry><refentrytitle>sd_bus_set_bus_client</refentrytitle><manvolnum>3</manvolnum></citerefentry>) the 142 match is only installed on the client side, and the synchronous and asynchronous functions operate the same.</para> 143 </refsect1> 144 145 <refsect1> 146 <title>Return Value</title> 147 148 <para> 149 On success, <function>sd_bus_add_match()</function> and the other calls return 0 or a positive integer. On 150 failure, they return a negative errno-style error code. 151 </para> 152 </refsect1> 153 154 <refsect1> 155 <title>Notes</title> 156 157 <xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/> 158 </refsect1> 159 160 <refsect1> 161 <title>See Also</title> 162 163 <para> 164 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, 165 <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, 166 <citerefentry><refentrytitle>sd_bus_slot_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>, 167 <citerefentry><refentrytitle>sd_bus_message_ref</refentrytitle><manvolnum>3</manvolnum></citerefentry>, 168 <citerefentry><refentrytitle>sd_bus_set_bus_client</refentrytitle><manvolnum>3</manvolnum></citerefentry>, 169 <citerefentry><refentrytitle>sd_bus_slot_set_floating</refentrytitle><manvolnum>3</manvolnum></citerefentry> 170 </para> 171 </refsect1> 172 173</refentry> 174