man/sd_bus_is_open.xml

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   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4
   5 <!--
   6   SPDX-License-Identifier: LGPL-2.1+
   7
   8   This file is part of systemd.
   9
  10   Copyright 2017 Lennart Poettering
  11 -->
  12
  13 <refentry id="sd_bus_is_open">
  14
  15   <refentryinfo>
  16     <title>sd_bus_is_open</title>
  17     <productname>systemd</productname>
  18
  19     <authorgroup>
  20       <author>
  21         <contrib>Developer</contrib>
  22         <firstname>Lennart</firstname>
  23         <surname>Poettering</surname>
  24         <email>lennart@poettering.net</email>
  25       </author>
  26     </authorgroup>
  27   </refentryinfo>
  28
  29   <refmeta>
  30     <refentrytitle>sd_bus_is_open</refentrytitle>
  31     <manvolnum>3</manvolnum>
  32   </refmeta>
  33
  34   <refnamediv>
  35     <refname>sd_bus_is_open</refname>
  36     <refname>sd_bus_is_ready</refname>
  37
  38     <refpurpose>Check whether the a bus connection is open or ready.</refpurpose>
  39   </refnamediv>
  40
  41   <refsynopsisdiv>
  42     <funcsynopsis>
  43       <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
  44
  45       <funcprototype>
  46         <funcdef>int <function>sd_bus_is_open</function></funcdef>
  47         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  48       </funcprototype>
  49
  50       <funcprototype>
  51         <funcdef>int <function>sd_bus_is_ready</function></funcdef>
  52         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  53       </funcprototype>
  54
  55     </funcsynopsis>
  56   </refsynopsisdiv>
  57
  58   <refsect1>
  59     <title>Description</title>
  60
  61     <para><function>sd_bus_is_open()</function> checks whether the specified bus connection is open, i.e. in the
  62     process of being established, already established or in the process of being torn down. It returns zero when the
  63     connection has not been started yet
  64     (i.e. <citerefentry><refentrytitle>sd_bus_start</refentrytitle><manvolnum>3</manvolnum></citerefentry> or some
  65     equivalent call has not been invoked yet), or is fully terminated again (for example after
  66     <citerefentry><refentrytitle>sd_bus_close</refentrytitle><manvolnum>3</manvolnum></citerefentry>), it returns
  67     positive otherwise.</para>
  68
  69     <para><function>sd_bus_is_ready()</function> checks whether the specified connection is fully established,
  70     i.e. completed the connection and authentication phases of the protocol and received the
  71     <function>Hello()</function> method call response, and is not in the process of being torn down again. It returns
  72     zero outside of this state, and positive otherwise. Effectively, this function returns positive while regular
  73     messages can be sent or received on the connection.</para>
  74
  75     <para>To be notified when the connection is fully established, use
  76     <citerefentry><refentrytitle>sd_bus_set_connected_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry> and
  77     install a match for the <function>Connected()</function> signal on the
  78     <literal>org.freedesktop.DBus.Local</literal> interface. To be notified when the connection is torn down again,
  79     install a match for the <function>Disconnected()</function> signal on the
  80     <literal>org.freedesktop.DBus.Local</literal> interface.</para>
  81   </refsect1>
  82
  83   <refsect1>
  84     <title>Return Value</title>
  85
  86     <para>On success, these functions return 0 or a positive integer. On failure, they return a negative errno-style
  87     error code.</para>
  88   </refsect1>
  89
  90   <refsect1>
  91     <title>Errors</title>
  92
  93     <para>Returned errors may indicate the following problems:</para>
  94
  95     <variablelist>
  96       <varlistentry>
  97         <term><constant>-ECHILD</constant></term>
  98
  99         <listitem><para>The bus connection has been created in a different process.</para></listitem>
 100       </varlistentry>
 101     </variablelist>
 102   </refsect1>
 103
 104   <refsect1>
 105     <title>Notes</title>
 106
 107     <para><function>sd_bus_is_open()</function> and <function>sd_bus_is_ready()</function> are available as
 108     a shared library, which can be compiled and linked to with the <constant>libsystemd</constant> <citerefentry
 109     project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> file.</para>
 110   </refsect1>
 111
 112   <refsect1>
 113     <title>See Also</title>
 114
 115     <para>
 116       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 117       <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 118       <citerefentry><refentrytitle>sd_bus_start</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 119       <citerefentry><refentrytitle>sd_bus_close</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 120       <citerefentry><refentrytitle>sd_bus_set_connected_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 121     </para>
 122   </refsect1>
 123
 124 </refentry>