man/sd_bus_is_open.xml

   1 <?xml version='1.0'?>
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
   4 <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
   5
   6 <refentry id="sd_bus_is_open"
   7           xmlns:xi="http://www.w3.org/2001/XInclude">
   8
   9   <refentryinfo>
  10     <title>sd_bus_is_open</title>
  11     <productname>systemd</productname>
  12   </refentryinfo>
  13
  14   <refmeta>
  15     <refentrytitle>sd_bus_is_open</refentrytitle>
  16     <manvolnum>3</manvolnum>
  17   </refmeta>
  18
  19   <refnamediv>
  20     <refname>sd_bus_is_open</refname>
  21     <refname>sd_bus_is_ready</refname>
  22
  23     <refpurpose>Check whether the bus connection is open or ready</refpurpose>
  24   </refnamediv>
  25
  26   <refsynopsisdiv>
  27     <funcsynopsis>
  28       <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
  29
  30       <funcprototype>
  31         <funcdef>int <function>sd_bus_is_open</function></funcdef>
  32         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  33       </funcprototype>
  34
  35       <funcprototype>
  36         <funcdef>int <function>sd_bus_is_ready</function></funcdef>
  37         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  38       </funcprototype>
  39
  40     </funcsynopsis>
  41   </refsynopsisdiv>
  42
  43   <refsect1>
  44     <title>Description</title>
  45
  46     <para><function>sd_bus_is_open()</function> checks whether the specified bus connection is open, i.e. in the
  47     process of being established, already established or in the process of being torn down. It returns zero when the
  48     connection has not been started yet
  49     (i.e. <citerefentry><refentrytitle>sd_bus_start</refentrytitle><manvolnum>3</manvolnum></citerefentry> or some
  50     equivalent call has not been invoked yet), or is fully terminated again (for example after
  51     <citerefentry><refentrytitle>sd_bus_close</refentrytitle><manvolnum>3</manvolnum></citerefentry>), it returns
  52     positive otherwise.</para>
  53
  54     <para><function>sd_bus_is_ready()</function> checks whether the specified connection is fully established,
  55     i.e. completed the connection and authentication phases of the protocol and received the
  56     <function>Hello()</function> method call response, and is not in the process of being torn down again. It returns
  57     zero outside of this state, and positive otherwise. Effectively, this function returns positive while regular
  58     messages can be sent or received on the connection.</para>
  59
  60     <para>The <parameter>bus</parameter> argument may be <constant>NULL</constant>, zero is also returned in
  61     that case.</para>
  62
  63     <para>To be notified when the connection is fully established, use
  64     <citerefentry><refentrytitle>sd_bus_set_connected_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry> and
  65     install a match for the <function>Connected()</function> signal on the
  66     <literal>org.freedesktop.DBus.Local</literal> interface. To be notified when the connection is torn down again,
  67     install a match for the <function>Disconnected()</function> signal on the
  68     <literal>org.freedesktop.DBus.Local</literal> interface.</para>
  69   </refsect1>
  70
  71   <refsect1>
  72     <title>Return Value</title>
  73
  74     <para>Those functions return 0 if the bus is <emphasis>not</emphasis> in the given state, and a positive
  75     integer when it is. On failure, a negative errno-style error code is returned.</para>
  76
  77     <refsect2>
  78       <title>Errors</title>
  79
  80       <para>Returned errors may indicate the following problems:</para>
  81
  82       <variablelist>
  83         <varlistentry>
  84           <term><constant>-ECHILD</constant></term>
  85
  86           <listitem><para>The bus connection has been created in a different process, library or module instance.</para></listitem>
  87         </varlistentry>
  88       </variablelist>
  89     </refsect2>
  90   </refsect1>
  91
  92   <xi:include href="libsystemd-pkgconfig.xml" />
  93
  94   <refsect1>
  95     <title>History</title>
  96     <para><function>sd_bus_is_open()</function> and
  97     <function>sd_bus_is_ready()</function> were added in version 237.</para>
  98   </refsect1>
  99
 100   <refsect1>
 101     <title>See Also</title>
 102
 103     <para><simplelist type="inline">
 104       <member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
 105       <member><citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
 106       <member><citerefentry><refentrytitle>sd_bus_start</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
 107       <member><citerefentry><refentrytitle>sd_bus_close</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
 108       <member><citerefentry><refentrytitle>sd_bus_set_connected_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
 109     </simplelist></para>
 110   </refsect1>
 111
 112 </refentry>