man: document sd_bus_close() + sd_bus_flush()

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

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

  <refentryinfo>
    <title>sd_bus_close</title>
    <productname>systemd</productname>
  </refentryinfo>

  <refmeta>
    <refentrytitle>sd_bus_close</refentrytitle>
    <manvolnum>3</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>sd_bus_close</refname>
    <refname>sd_bus_flush</refname>

    <refpurpose>Close and flush a bus connection</refpurpose>
  </refnamediv>

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

      <funcprototype>
        <funcdef>void <function>sd_bus_close</function></funcdef>
        <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
      </funcprototype>

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

  <refsect1>
    <title>Description</title>

    <para><function>sd_bus_close()</function> disconnects the specified bus connection. When this call is invoked and
    the specified bus object refers to an active connection it is immediately terminated. No further messages may be
    sent or receieved on it. Any messages queued in the bus object (both incoming and outgoing) are released. If
    invoked on <constant>NULL</constant> bus object or when the bus connection is already closed this function executes
    no operation. This call does not free or unreference the bus object itself. Use
    <citerefentry><refentrytitle>sd_bus_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> for that.</para>

    <para><function>sd_bus_flush()</function> synchronously writes out all outgoing queued message on a bus connection
    if there are any. This function call may block if the peer is not processing bus messages quickly.</para>

    <para>Before a program exits it is usually a good idea to flush any pending messages with
    <function>sd_bus_flush()</function> and then close connections with <function>sd_bus_close()</function> to ensure
    that no unwritten messages are lost, no further messages may be queued and all incoming but unprocessed messages
    are released. After both operations have been done, it is a good idea to also drop any remaining references to the
    bus object so that it may be freed. Since these three operations are frequently done together a helper call
    <citerefentry><refentrytitle>sd_bus_flush_close_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry> is
    provided that combines them into one.</para>
  </refsect1>

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

    <para>On success, <function>sd_bus_flush()</function> returns 0 or a positive integer. On failure, it returns 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>

  <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_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd_bus_set_close_on_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    </para>
  </refsect1>

</refentry>