man/sd_bus_set_watch_bind.xml

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