systemd/man/sd_bus_start.xml

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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->

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

  <refentryinfo>
    <title>sd_bus_start</title>
    <productname>systemd</productname>
  </refentryinfo>

  <refmeta>
    <refentrytitle>sd_bus_start</refentrytitle>
    <manvolnum>3</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>sd_bus_start</refname>

    <refpurpose>Initiate a bus connection to the D-bus broker daemon
    </refpurpose>
  </refnamediv>

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

      <funcprototype>
        <funcdef>int <function>sd_bus_start</function></funcdef>
        <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
      </funcprototype>
    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para><function>sd_bus_start()</function> connects an existing bus connection object to the D-Bus
    broker daemon, usually
    <citerefentry project='die-net'><refentrytitle>dbus-daemon</refentrytitle><manvolnum>1</manvolnum></citerefentry>
    or
    <citerefentry project='mankier'><refentrytitle>dbus-broker</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
    The mechanism to use for the connection must be configured before the call to
    <function>sd_bus_start()</function>, using one of
    <citerefentry><refentrytitle>sd_bus_set_address</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
    <citerefentry><refentrytitle>sd_bus_set_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry>, or
    <citerefentry><refentrytitle>sd_bus_set_exec</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
    <function>sd_bus_start()</function> will open the connection socket or spawn the executable as
    needed, and asynchronously start a <function>org.freedesktop.DBus.Hello()</function> call. The
    answer to the Hello call will be processed later from
    <citerefentry><refentrytitle>sd_bus_process</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If
    opening of the connection or queuing of the asynchronous call fail, the connection will be closed with
    <citerefentry><refentrytitle>sd_bus_close</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>

    <para>In most cases, it is better to use
    <citerefentry><refentrytitle>sd_bus_default_user</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
    <citerefentry><refentrytitle>sd_bus_default_system</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    or related calls instead of the more low-level <function>sd_bus_new()</function> and
    <function>sd_bus_start()</function>. The higher-level functions not only allocate a bus object but also
    start the connection to a well-known bus in a single function call.</para>
  </refsect1>

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

    <para>On success, this function returns a non-negative integer. On failure, it returns a negative
    errno-style error code.</para>

    <refsect2 id='errors'>
      <title>Errors</title>

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

          <listitem><para>The input parameter <parameter>bus</parameter> is <constant>NULL</constant>.
          </para></listitem>
        </varlistentry>

        <varlistentry>
          <term><constant>-ENOPKG</constant></term>

          <listitem><para>Bus object <parameter>bus</parameter> could not be resolved.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term><constant>-EPERM</constant></term>

          <listitem><para>The input parameter <parameter>bus</parameter> is in a wrong state
          (<function>sd_bus_start()</function> may only be called once on a newly-created bus object).</para>
          </listitem>
        </varlistentry>

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

          <listitem><para>The bus object <parameter>bus</parameter> was created in a different
          process.</para>
          </listitem>
        </varlistentry>
      </variablelist>

      <para>In addition, other connection-related errors may be returned. See
      <citerefentry><refentrytitle>sd_bus_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
    </refsect2>
  </refsect1>

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

  <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_default</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_bus_call_async</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    </para>
  </refsect1>

</refentry>