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

  <refentryinfo>
    <title>sd_bus_is_open</title>
    <productname>systemd</productname>
  </refentryinfo>

  <refmeta>
    <refentrytitle>sd_bus_is_open</refentrytitle>
    <manvolnum>3</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>sd_bus_is_open</refname>
    <refname>sd_bus_is_ready</refname>

    <refpurpose>Check whether the bus connection is open or ready</refpurpose>
  </refnamediv>

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

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

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

    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para><function>sd_bus_is_open()</function> checks whether the specified bus connection is open, i.e. in the
    process of being established, already established or in the process of being torn down. It returns zero when the
    connection has not been started yet
    (i.e. <citerefentry><refentrytitle>sd_bus_start</refentrytitle><manvolnum>3</manvolnum></citerefentry> or some
    equivalent call has not been invoked yet), or is fully terminated again (for example after
    <citerefentry><refentrytitle>sd_bus_close</refentrytitle><manvolnum>3</manvolnum></citerefentry>), it returns
    positive otherwise.</para>

    <para><function>sd_bus_is_ready()</function> checks whether the specified connection is fully established,
    i.e. completed the connection and authentication phases of the protocol and received the
    <function>Hello()</function> method call response, and is not in the process of being torn down again. It returns
    zero outside of this state, and positive otherwise. Effectively, this function returns positive while regular
    messages can be sent or received on the connection.</para>

    <para>The <parameter>bus</parameter> argument may be <constant>NULL</constant>, zero is also returned in
    that case.</para>

    <para>To be notified when the connection is fully established, use
    <citerefentry><refentrytitle>sd_bus_set_connected_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry> and
    install a match for the <function>Connected()</function> signal on the
    <literal>org.freedesktop.DBus.Local</literal> interface. To be notified when the connection is torn down again,
    install a match for the <function>Disconnected()</function> signal on the
    <literal>org.freedesktop.DBus.Local</literal> interface.</para>
  </refsect1>

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

    <para>Those functions return 0 if the bus is <emphasis>not</emphasis> in the given state, and a positive
    integer when it is. On failure, a negative errno-style error code is returned.</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_is_open()</function> and
    <function>sd_bus_is_ready()</function> were added in version 237.</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_start</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_bus_close</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_bus_set_connected_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    </para>
  </refsect1>

</refentry>