man/sd_bus_set_connected_signal.xml

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