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systemd/man/sd_bus_get_n_queued_read.xml
Zbigniew Jędrzejewski-Szmek 11a1589223 tree-wide: drop license boilerplate
Files which are installed as-is (any .service and other unit files, .conf
files, .policy files, etc), are left as is. My assumption is that SPDX
identifiers are not yet that well known, so it's better to retain the
extended header to avoid any doubt.

I also kept any copyright lines. We can probably remove them, but it'd nice to
obtain explicit acks from all involved authors before doing that.
2018-04-06 18:58:55 +02:00

117 lines
4.2 KiB
XML

<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
SPDX-License-Identifier: LGPL-2.1+
This file is part of systemd.
Copyright 2018 Lennart Poettering
-->
<refentry id="sd_bus_get_n_queued_read">
<refentryinfo>
<title>sd_bus_get_fd</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>Developer</contrib>
<firstname>Lennart</firstname>
<surname>Poettering</surname>
<email>lennart@poettering.net</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>sd_bus_get_n_queued_read</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>sd_bus_get_n_queued_read</refname>
<refname>sd_bus_get_n_queued_write</refname>
<refpurpose>Get the number of pending bus messages in the read and write queues of a bus connection object</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
<funcprototype>
<funcdef>int <function>sd_bus_get_n_queued_read</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>uint64_t *<parameter>ret</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_bus_get_n_queued_write</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>uint64_t *<parameter>ret</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>
<function>sd_bus_get_n_queued_read()</function> may be used to query the number of bus messages in the read queue
of a bus connection object. The read queue contains all messages read from the transport medium (e.g. network
socket) but not yet processed locally. The function expects two arguments: the bus object to query, and a pointer
to a 64bit counter variable to write the current queue size to. Use <function>sd_bus_process()</function> in
order to process queued messages, i.e. to reduce the size of the read queue (as well as, in fact, the write
queue, see below).
</para>
<para>
Similarly, <function>sd_bus_get_n_queued_write()</function> may be used to query the number of currently pending
bus messages in the write queue of a bus connection object. The write queue contains all messages enqueued into
the connection with a call such as <function>sd_bus_send()</function> but not yet written to the transport
medium. The expected arguments are similar to <function>sd_bus_get_n_queued_read()</function>. Here too, use
<function>sd_bus_process()</function> to reduce the size of the write queue. Alternatively, use
<function>sd_bus_flush()</function> to synchronously write out any pending bus messages until the write queue is
empty.
</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para>On success, these functions return 0 or a positive integer. On failure, they return a negative errno-style
error code.</para>
</refsect1>
<refsect1>
<title>Errors</title>
<para>Returned errors may indicate the following problems:</para>
<variablelist>
<varlistentry>
<term><constant>-ECHILD</constant></term>
<listitem><para>The bus connection was created in a different process.</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_process</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_bus_flush</refentrytitle><manvolnum>3</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>