man/sd_bus_get_n_queued_read.xml

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   5 <!--
   6   SPDX-License-Identifier: LGPL-2.1+
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   8
   9 <refentry id="sd_bus_get_n_queued_read">
  10
  11   <refentryinfo>
  12     <title>sd_bus_get_fd</title>
  13     <productname>systemd</productname>
  14   </refentryinfo>
  15
  16   <refmeta>
  17     <refentrytitle>sd_bus_get_n_queued_read</refentrytitle>
  18     <manvolnum>3</manvolnum>
  19   </refmeta>
  20
  21   <refnamediv>
  22     <refname>sd_bus_get_n_queued_read</refname>
  23     <refname>sd_bus_get_n_queued_write</refname>
  24
  25     <refpurpose>Get the number of pending bus messages in the read and write queues of a bus connection object</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_get_n_queued_read</function></funcdef>
  34         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  35         <paramdef>uint64_t *<parameter>ret</parameter></paramdef>
  36       </funcprototype>
  37
  38       <funcprototype>
  39         <funcdef>int <function>sd_bus_get_n_queued_write</function></funcdef>
  40         <paramdef>sd_bus *<parameter>bus</parameter></paramdef>
  41         <paramdef>uint64_t *<parameter>ret</parameter></paramdef>
  42       </funcprototype>
  43     </funcsynopsis>
  44   </refsynopsisdiv>
  45
  46   <refsect1>
  47     <title>Description</title>
  48
  49     <para>
  50       <function>sd_bus_get_n_queued_read()</function> may be used to query the number of bus messages in the read queue
  51       of a bus connection object. The read queue contains all messages read from the transport medium (e.g. network
  52       socket) but not yet processed locally. The function expects two arguments: the bus object to query, and a pointer
  53       to a 64bit counter variable to write the current queue size to. Use <function>sd_bus_process()</function> in
  54       order to process queued messages, i.e. to reduce the size of the read queue (as well as, in fact, the write
  55       queue, see below).
  56     </para>
  57
  58     <para>
  59       Similarly, <function>sd_bus_get_n_queued_write()</function> may be used to query the number of currently pending
  60       bus messages in the write queue of a bus connection object. The write queue contains all messages enqueued into
  61       the connection with a call such as <function>sd_bus_send()</function> but not yet written to the transport
  62       medium. The expected arguments are similar to <function>sd_bus_get_n_queued_read()</function>. Here too, use
  63       <function>sd_bus_process()</function> to reduce the size of the write queue. Alternatively, use
  64       <function>sd_bus_flush()</function> to synchronously write out any pending bus messages until the write queue is
  65       empty.
  66     </para>
  67   </refsect1>
  68
  69   <refsect1>
  70     <title>Return Value</title>
  71
  72     <para>On success, these functions return 0 or a positive integer. On failure, they return a negative errno-style
  73     error code.</para>
  74   </refsect1>
  75
  76   <refsect1>
  77     <title>Errors</title>
  78
  79     <para>Returned errors may indicate the following problems:</para>
  80
  81     <variablelist>
  82       <varlistentry>
  83         <term><constant>-ECHILD</constant></term>
  84
  85         <listitem><para>The bus connection was created in a different process.</para></listitem>
  86       </varlistentry>
  87
  88     </variablelist>
  89   </refsect1>
  90
  91   <refsect1>
  92     <title>See Also</title>
  93
  94     <para>
  95       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
  96       <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  97       <citerefentry><refentrytitle>sd_bus_process</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  98       <citerefentry><refentrytitle>sd_bus_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
  99       <citerefentry><refentrytitle>sd_bus_flush</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 100     </para>
 101   </refsect1>
 102
 103 </refentry>