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