man/sd_bus_set_watch_bind.xml

   1 <?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
   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 elogind.
   9
  10   Copyright 2017 Lennart Poettering
  11 -->
  12
  13 <refentry id="sd_bus_set_watch_bind">
  14
  15   <refentryinfo>
  16     <title>sd_bus_set_watch_bind</title>
  17     <productname>elogind</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_set_watch_bind</refentrytitle>
  31     <manvolnum>3</manvolnum>
  32   </refmeta>
  33
  34   <refnamediv>
  35     <refname>sd_bus_set_watch_bind</refname>
  36     <refname>sd_bus_get_watch_bind</refname>
  37
  38     <refpurpose>Control socket binding watching on bus connections</refpurpose>
  39   </refnamediv>
  40
  41   <refsynopsisdiv>
  42     <funcsynopsis>
  43       <funcsynopsisinfo>#include &lt;elogind/sd-bus.h&gt;</funcsynopsisinfo>
  44
  45       <funcprototype>
  46         <funcdef>int <function>sd_bus_set_watch_bind</function></funcdef>
  47         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  48         <paramdef>int <parameter>b</parameter></paramdef>
  49       </funcprototype>
  50
  51       <funcprototype>
  52         <funcdef>int <function>sd_bus_get_watch_bind</function></funcdef>
  53         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  54       </funcprototype>
  55
  56     </funcsynopsis>
  57   </refsynopsisdiv>
  58
  59   <refsect1>
  60     <title>Description</title>
  61
  62     <para><function>sd_bus_set_watch_bind()</function> may be used to enable or disable client-side watching of server
  63     socket binding for a bus connection object. If the <parameter>b</parameter> is true, the feature is enabled,
  64     otherwise disabled (which is the default). When enabled, and the selected bus address refers to an
  65     <filename>AF_UNIX</filename> socket in the file system which does not exist while the connection attempt is made an
  66     <citerefentry><refentrytitle>inotify</refentrytitle><manvolnum>7</manvolnum></citerefentry> watch is installed on
  67     it, waiting for the socket to appear. As soon as the socket appears the connection is made. This functionality is
  68     useful in particular in early-boot programs that need to run before the system bus is available, but want to
  69     connect to it the instant it may be connected to.</para>
  70
  71     <para><function>sd_bus_get_watch_bind()</function> may be used to query the current setting of this feature. It
  72     returns zero when the feature is disabled, and positive if enabled.</para>
  73
  74     <para>Note that no timeout is applied while it is waited for the socket to appear. This means that any synchronous
  75     remote operation (such as
  76     <citerefentry><refentrytitle>sd_bus_call</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  77     <citerefentry><refentrytitle>sd_bus_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry> or
  78     <citerefentry><refentrytitle>sd_bus_request_name</refentrytitle><manvolnum>3</manvolnum></citerefentry>), that is
  79     used on a connection with this feature enabled that is not established yet might block unbounded if the socket is
  80     never created. However, asynchronous remote operations (such as
  81     <citerefentry><refentrytitle>sd_bus_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  82     <citerefentry><refentrytitle>sd_bus_add_match_async</refentrytitle><manvolnum>3</manvolnum></citerefentry> or
  83     <citerefentry><refentrytitle>sd_bus_request_match_async</refentrytitle><manvolnum>3</manvolnum></citerefentry>) do
  84     not block in this case, and safely enqueue the requested operations to be dispatched the instant the connection is
  85     set up.</para>
  86
  87     <para>Use <citerefentry><refentrytitle>sd_bus_is_ready</refentrytitle><manvolnum>3</manvolnum></citerefentry> to
  88     determine whether the connection is fully established, i.e. whether the peer socket has been bound, connected to
  89     and authenticated. Use
  90     <citerefentry><refentrytitle>sd_bus_set_connected_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry> to
  91     be notified when the connection is fully established.</para>
  92
  93   </refsect1>
  94
  95   <refsect1>
  96     <title>Return Value</title>
  97
  98     <para>On success, these functions return 0 or a positive integer. On failure, they return a negative errno-style
  99     error code.</para>
 100   </refsect1>
 101
 102   <refsect1>
 103     <title>Errors</title>
 104
 105     <para>Returned errors may indicate the following problems:</para>
 106
 107     <variablelist>
 108       <varlistentry>
 109         <term><constant>-ECHILD</constant></term>
 110
 111         <listitem><para>The bus connection has been created in a different process.</para></listitem>
 112       </varlistentry>
 113     </variablelist>
 114   </refsect1>
 115
 116   <refsect1>
 117     <title>Notes</title>
 118
 119     <para><function>sd_bus_set_watch_bind()</function> and <function>sd_bus_get_watch_bind()</function> are available as
 120     a shared library, which can be compiled and linked to with the <constant>libelogind</constant> <citerefentry
 121     project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> file.</para>
 122   </refsect1>
 123
 124   <refsect1>
 125     <title>See Also</title>
 126
 127     <para>
 128       <citerefentry><refentrytitle>elogind</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 129       <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 130       <citerefentry><refentrytitle>inotify</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 131       <citerefentry><refentrytitle>sd_bus_call</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 132       <citerefentry><refentrytitle>sd_bus_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 133       <citerefentry><refentrytitle>sd_bus_request_name</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 134       <citerefentry><refentrytitle>sd_bus_is_ready</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 135       <citerefentry><refentrytitle>sd_bus_set_connected_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 136     </para>
 137   </refsect1>
 138
 139 </refentry>