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[thirdparty/systemd.git] / man / sd_bus_set_connected_signal.xml

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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
  "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->

<refentry id="sd_bus_set_connected_signal"
          xmlns:xi="http://www.w3.org/2001/XInclude">

  <refentryinfo>
    <title>sd_bus_set_connected_signal</title>
    <productname>systemd</productname>
  </refentryinfo>

  <refmeta>
    <refentrytitle>sd_bus_set_connected_signal</refentrytitle>
    <manvolnum>3</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>sd_bus_set_connected_signal</refname>
    <refname>sd_bus_get_connected_signal</refname>

    <refpurpose>Control emission of local connection establishment signal on bus connections</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <funcsynopsis>
      <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>

      <funcprototype>
        <funcdef>int <function>sd_bus_set_connected_signal</function></funcdef>
        <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
        <paramdef>int <parameter>b</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int <function>sd_bus_get_connected_signal</function></funcdef>
        <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
      </funcprototype>

    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para><function>sd_bus_set_connected_signal()</function> may be used to control whether a local, synthetic
    <function>Connected()</function> signal message shall be generated and enqueued for dispatching when the connection
    is fully established. If the <parameter>b</parameter> parameter is zero the message is not generated (the default),
    otherwise it is generated.</para>

    <para><function>sd_bus_get_connected_signal()</function> may be used to query whether this feature is enabled. It
    returns zero if not, positive otherwise.</para>

    <para>The <function>Connected()</function> signal message is generated from the
    <literal>org.freedesktop.DBus.Local</literal> service and interface, and
    <literal>/org/freedesktop/DBus/Local</literal> object path. Use
    <citerefentry><refentrytitle>sd_bus_match_signal_async</refentrytitle><manvolnum>3</manvolnum></citerefentry> to
    match on this signal.</para>

    <para>This message is particularly useful on slow transports where connections take a long time to be
    established. This is especially the case when
    <citerefentry><refentrytitle>sd_bus_set_watch_bind</refentrytitle><manvolnum>3</manvolnum></citerefentry> is
    used. The signal is generated when the
    <citerefentry><refentrytitle>sd_bus_is_ready</refentrytitle><manvolnum>3</manvolnum></citerefentry> returns
    positive for the first time.</para>

    <para>The <function>Connected()</function> signal corresponds with the <function>Disconnected()</function> signal
    that is synthesized locally when the connection is terminated. The latter is generated unconditionally however,
    unlike the former which needs to be enabled explicitly before it is generated, with
    <function>sd_bus_set_connected_signal()</function>.</para>
  </refsect1>

  <refsect1>
    <title>Return Value</title>

    <para>On success, these functions return 0 or a positive integer. On failure, they return a negative
    errno-style error code.</para>

    <refsect2>
      <title>Errors</title>

      <para>Returned errors may indicate the following problems:</para>

      <variablelist>
        <varlistentry>
          <term><constant>-ECHILD</constant></term>

          <listitem><para>The bus connection has been created in a different process, library or module instance.</para></listitem>
        </varlistentry>
      </variablelist>
    </refsect2>
  </refsect1>

  <xi:include href="libsystemd-pkgconfig.xml" />

  <refsect1>
    <title>History</title>
    <para><function>sd_bus_set_connected_signal()</function> and
    <function>sd_bus_get_connected_signal()</function> were added in version 237.</para>
  </refsect1>

  <refsect1>
    <title>See Also</title>

    <para><simplelist type="inline">
      <member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
      <member><citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
      <member><citerefentry><refentrytitle>sd_bus_match_signal_async</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
      <member><citerefentry><refentrytitle>sd_bus_set_watch_bind</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
      <member><citerefentry><refentrytitle>sd_bus_is_ready</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
    </simplelist></para>
  </refsect1>

</refentry>