man/sd_bus_set_connected_signal.xml

<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">

<!--
  SPDX-License-Identifier: LGPL-2.1+

  This file is part of systemd.

  Copyright 2017 Lennart Poettering

  systemd is free software; you can redistribute it and/or modify it
  under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation; either version 2.1 of the License, or
  (at your option) any later version.

  systemd is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->

<refentry id="sd_bus_set_connected_signal">

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

    <authorgroup>
      <author>
        <contrib>Developer</contrib>
        <firstname>Lennart</firstname>
        <surname>Poettering</surname>
        <email>lennart@poettering.net</email>
      </author>
    </authorgroup>
  </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 emmission 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>
  </refsect1>

  <refsect1>
    <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.</para></listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Notes</title>

    <para><function>sd_bus_set_connected_signal()</function> and <function>sd_bus_get_connected_signal()</function> are available as
    a shared library, which can be compiled and linked to with the <constant>libsystemd</constant> <citerefentry
    project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> file.</para>
  </refsect1>

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

    <para>
      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_bus_match_signal_async</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_bus_set_watch_bind</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_bus_is_ready</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    </para>
  </refsect1>

</refentry>