man/sd_bus_set_watch_bind.xml

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   6   SPDX-License-Identifier: LGPL-2.1+
   7 -->
   8
   9 <refentry id="sd_bus_set_watch_bind">
  10
  11   <refentryinfo>
  12     <title>sd_bus_set_watch_bind</title>
  13     <productname>elogind</productname>
  14
  15     <authorgroup>
  16       <author>
  17         <contrib>Developer</contrib>
  18         <firstname>Lennart</firstname>
  19         <surname>Poettering</surname>
  20         <email>lennart@poettering.net</email>
  21       </author>
  22     </authorgroup>
  23   </refentryinfo>
  24
  25   <refmeta>
  26     <refentrytitle>sd_bus_set_watch_bind</refentrytitle>
  27     <manvolnum>3</manvolnum>
  28   </refmeta>
  29
  30   <refnamediv>
  31     <refname>sd_bus_set_watch_bind</refname>
  32     <refname>sd_bus_get_watch_bind</refname>
  33
  34     <refpurpose>Control socket binding watching on bus connections</refpurpose>
  35   </refnamediv>
  36
  37   <refsynopsisdiv>
  38     <funcsynopsis>
  39       <funcsynopsisinfo>#include &lt;elogind/sd-bus.h&gt;</funcsynopsisinfo>
  40
  41       <funcprototype>
  42         <funcdef>int <function>sd_bus_set_watch_bind</function></funcdef>
  43         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  44         <paramdef>int <parameter>b</parameter></paramdef>
  45       </funcprototype>
  46
  47       <funcprototype>
  48         <funcdef>int <function>sd_bus_get_watch_bind</function></funcdef>
  49         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  50       </funcprototype>
  51
  52     </funcsynopsis>
  53   </refsynopsisdiv>
  54
  55   <refsect1>
  56     <title>Description</title>
  57
  58     <para><function>sd_bus_set_watch_bind()</function> may be used to enable or disable client-side watching of server
  59     socket binding for a bus connection object. If the <parameter>b</parameter> is true, the feature is enabled,
  60     otherwise disabled (which is the default). When enabled, and the selected bus address refers to an
  61     <filename>AF_UNIX</filename> socket in the file system which does not exist while the connection attempt is made an
  62     <citerefentry><refentrytitle>inotify</refentrytitle><manvolnum>7</manvolnum></citerefentry> watch is installed on
  63     it, waiting for the socket to appear. As soon as the socket appears the connection is made. This functionality is
  64     useful in particular in early-boot programs that need to run before the system bus is available, but want to
  65     connect to it the instant it may be connected to.</para>
  66
  67     <para><function>sd_bus_get_watch_bind()</function> may be used to query the current setting of this feature. It
  68     returns zero when the feature is disabled, and positive if enabled.</para>
  69
  70     <para>Note that no timeout is applied while it is waited for the socket to appear. This means that any synchronous
  71     remote operation (such as
  72     <citerefentry><refentrytitle>sd_bus_call</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  73     <citerefentry><refentrytitle>sd_bus_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry> or
  74     <citerefentry><refentrytitle>sd_bus_request_name</refentrytitle><manvolnum>3</manvolnum></citerefentry>), that is
  75     used on a connection with this feature enabled that is not established yet might block unbounded if the socket is
  76     never created. However, asynchronous remote operations (such as
  77     <citerefentry><refentrytitle>sd_bus_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  78     <citerefentry><refentrytitle>sd_bus_add_match_async</refentrytitle><manvolnum>3</manvolnum></citerefentry> or
  79     <citerefentry><refentrytitle>sd_bus_request_match_async</refentrytitle><manvolnum>3</manvolnum></citerefentry>) do
  80     not block in this case, and safely enqueue the requested operations to be dispatched the instant the connection is
  81     set up.</para>
  82
  83     <para>Use <citerefentry><refentrytitle>sd_bus_is_ready</refentrytitle><manvolnum>3</manvolnum></citerefentry> to
  84     determine whether the connection is fully established, i.e. whether the peer socket has been bound, connected to
  85     and authenticated. Use
  86     <citerefentry><refentrytitle>sd_bus_set_connected_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry> to
  87     be notified when the connection is fully established.</para>
  88
  89   </refsect1>
  90
  91   <refsect1>
  92     <title>Return Value</title>
  93
  94     <para>On success, these functions return 0 or a positive integer. On failure, they return a negative errno-style
  95     error code.</para>
  96   </refsect1>
  97
  98   <refsect1>
  99     <title>Errors</title>
 100
 101     <para>Returned errors may indicate the following problems:</para>
 102
 103     <variablelist>
 104       <varlistentry>
 105         <term><constant>-ECHILD</constant></term>
 106
 107         <listitem><para>The bus connection has been created in a different process.</para></listitem>
 108       </varlistentry>
 109     </variablelist>
 110   </refsect1>
 111
 112   <refsect1>
 113     <title>Notes</title>
 114
 115     <para><function>sd_bus_set_watch_bind()</function> and <function>sd_bus_get_watch_bind()</function> are available as
 116     a shared library, which can be compiled and linked to with the <constant>libelogind</constant> <citerefentry
 117     project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> file.</para>
 118   </refsect1>
 119
 120   <refsect1>
 121     <title>See Also</title>
 122
 123     <para>
 124       <citerefentry><refentrytitle>elogind</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 125       <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 126       <citerefentry><refentrytitle>inotify</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 127       <citerefentry><refentrytitle>sd_bus_call</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 128       <citerefentry><refentrytitle>sd_bus_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 129       <citerefentry><refentrytitle>sd_bus_request_name</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 130       <citerefentry><refentrytitle>sd_bus_is_ready</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 131       <citerefentry><refentrytitle>sd_bus_set_connected_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 132     </para>
 133   </refsect1>
 134
 135 </refentry>