man/sd_bus_set_connected_signal.xml

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   6   SPDX-License-Identifier: LGPL-2.1+
   7
   8   This file is part of systemd.
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  10   Copyright 2017 Lennart Poettering
  11 -->
  12
  13 <refentry id="sd_bus_set_connected_signal">
  14
  15   <refentryinfo>
  16     <title>sd_bus_set_connected_signal</title>
  17     <productname>systemd</productname>
  18
  19     <authorgroup>
  20       <author>
  21         <contrib>Developer</contrib>
  22         <firstname>Lennart</firstname>
  23         <surname>Poettering</surname>
  24         <email>lennart@poettering.net</email>
  25       </author>
  26     </authorgroup>
  27   </refentryinfo>
  28
  29   <refmeta>
  30     <refentrytitle>sd_bus_set_connected_signal</refentrytitle>
  31     <manvolnum>3</manvolnum>
  32   </refmeta>
  33
  34   <refnamediv>
  35     <refname>sd_bus_set_connected_signal</refname>
  36     <refname>sd_bus_get_connected_signal</refname>
  37
  38     <refpurpose>Control emmission of local connection establishment signal on bus connections</refpurpose>
  39   </refnamediv>
  40
  41   <refsynopsisdiv>
  42     <funcsynopsis>
  43       <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
  44
  45       <funcprototype>
  46         <funcdef>int <function>sd_bus_set_connected_signal</function></funcdef>
  47         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  48         <paramdef>int <parameter>b</parameter></paramdef>
  49       </funcprototype>
  50
  51       <funcprototype>
  52         <funcdef>int <function>sd_bus_get_connected_signal</function></funcdef>
  53         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  54       </funcprototype>
  55
  56     </funcsynopsis>
  57   </refsynopsisdiv>
  58
  59   <refsect1>
  60     <title>Description</title>
  61
  62     <para><function>sd_bus_set_connected_signal()</function> may be used to control whether a local, synthetic
  63     <function>Connected()</function> signal message shall be generated and enqueued for dispatching when the connection
  64     is fully established. If the <parameter>b</parameter> parameter is zero the message is not generated (the default),
  65     otherwise it is generated.</para>
  66
  67     <para><function>sd_bus_get_connected_signal()</function> may be used to query whether this feature is enabled. It
  68     returns zero if not, positive otherwise.</para>
  69
  70     <para>The <function>Connected()</function> signal message is generated from the
  71     <literal>org.freedesktop.DBus.Local</literal> service and interface, and
  72     <literal>/org/freedesktop/DBus/Local</literal> object path. Use
  73     <citerefentry><refentrytitle>sd_bus_match_signal_async</refentrytitle><manvolnum>3</manvolnum></citerefentry> to
  74     match on this signal.</para>
  75
  76     <para>This message is particularly useful on slow transports where connections take a long time to be
  77     established. This is especially the case when
  78     <citerefentry><refentrytitle>sd_bus_set_watch_bind</refentrytitle><manvolnum>3</manvolnum></citerefentry> is
  79     used. The signal is generated when the
  80     <citerefentry><refentrytitle>sd_bus_is_ready</refentrytitle><manvolnum>3</manvolnum></citerefentry> returns
  81     positive for the first time.</para>
  82
  83     <para>The <function>Connected()</function> signal corresponds with the <function>Disconnected()</function> signal
  84     that is synthesized locally when the connection is terminated. The latter is generated unconditionally however,
  85     unlike the former which needs to be enabled explicitly before it is generated, with
  86     <function>sd_bus_set_connected_signal()</function>.</para>
  87   </refsect1>
  88
  89   <refsect1>
  90     <title>Return Value</title>
  91
  92     <para>On success, these functions return 0 or a positive integer. On failure, they return a negative errno-style
  93     error code.</para>
  94   </refsect1>
  95
  96   <refsect1>
  97     <title>Errors</title>
  98
  99     <para>Returned errors may indicate the following problems:</para>
 100
 101     <variablelist>
 102       <varlistentry>
 103         <term><constant>-ECHILD</constant></term>
 104
 105         <listitem><para>The bus connection has been created in a different process.</para></listitem>
 106       </varlistentry>
 107     </variablelist>
 108   </refsect1>
 109
 110   <refsect1>
 111     <title>Notes</title>
 112
 113     <para><function>sd_bus_set_connected_signal()</function> and <function>sd_bus_get_connected_signal()</function> are available as
 114     a shared library, which can be compiled and linked to with the <constant>libsystemd</constant> <citerefentry
 115     project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> file.</para>
 116   </refsect1>
 117
 118   <refsect1>
 119     <title>See Also</title>
 120
 121     <para>
 122       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 123       <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 124       <citerefentry><refentrytitle>sd_bus_match_signal_async</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 125       <citerefentry><refentrytitle>sd_bus_set_watch_bind</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 126       <citerefentry><refentrytitle>sd_bus_is_ready</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 127     </para>
 128   </refsect1>
 129
 130 </refentry>