systemd/man/sd_bus_close.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_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>
    <refname>sd_bus_default_flush_close</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>

      <funcprototype>
        <funcdef>void <function>sd_bus_default_flush_close</function></funcdef>
        <paramdef>void</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 received 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>

    <para><function>sd_bus_default_flush_close()</function> is similar to
    <function>sd_bus_flush_close_unref()</function>, but does not take a bus pointer argument and
    instead iterates over any of the "default" buses opened by
    <citerefentry><refentrytitle>sd_bus_default</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
    <citerefentry><refentrytitle>sd_bus_default_user</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
    <citerefentry><refentrytitle>sd_bus_default_system</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
    and similar calls. <function>sd_bus_default_flush_close()</function> is particularly useful to
    clean up any buses opened using those calls before the program exits.</para>
  </refsect1>

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

    <para>On success, <function>sd_bus_flush()</function> returns a non-negative integer. On
    failure, it returns 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_close()</function> and
    <function>sd_bus_flush()</function> were added in version 221.</para>
    <para><function>sd_bus_default_flush_close()</function> was added in version 227.</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_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
      <member><citerefentry><refentrytitle>sd_bus_set_close_on_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
    </simplelist></para>
  </refsect1>

</refentry>