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https://github.com/systemd/systemd
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107 lines
4.2 KiB
XML
107 lines
4.2 KiB
XML
<?xml version='1.0'?>
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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<refentry id="sd_bus_get_n_queued_read">
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<refentryinfo>
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<title>sd_bus_get_fd</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>sd_bus_get_n_queued_read</refentrytitle>
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<manvolnum>3</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>sd_bus_get_n_queued_read</refname>
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<refname>sd_bus_get_n_queued_write</refname>
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<refpurpose>Get the number of pending bus messages in the read and write queues of a bus connection object</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
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<funcprototype>
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<funcdef>int <function>sd_bus_get_n_queued_read</function></funcdef>
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<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
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<paramdef>uint64_t *<parameter>ret</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_bus_get_n_queued_write</function></funcdef>
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<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
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<paramdef>uint64_t *<parameter>ret</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para>
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<function>sd_bus_get_n_queued_read()</function> may be used to query the number of bus messages in the read queue
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of a bus connection object. The read queue contains all messages read from the transport medium (e.g. network
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socket) but not yet processed locally. The function expects two arguments: the bus object to query, and a pointer
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to a 64-bit counter variable to write the current queue size to. Use <function>sd_bus_process()</function> in
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order to process queued messages, i.e. to reduce the size of the read queue (as well as, in fact, the write
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queue, see below).
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</para>
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<para>
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Similarly, <function>sd_bus_get_n_queued_write()</function> may be used to query the number of currently pending
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bus messages in the write queue of a bus connection object. The write queue contains all messages enqueued into
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the connection with a call such as <function>sd_bus_send()</function> but not yet written to the transport
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medium. The expected arguments are similar to <function>sd_bus_get_n_queued_read()</function>. Here too, use
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<function>sd_bus_process()</function> to reduce the size of the write queue. Alternatively, use
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<function>sd_bus_flush()</function> to synchronously write out any pending bus messages until the write queue is
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empty.
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</para>
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</refsect1>
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<refsect1>
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<title>Return Value</title>
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<para>On success, these functions return 0 or a positive integer. On failure, they return a negative errno-style
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error code.</para>
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<refsect2>
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<title>Errors</title>
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<para>Returned errors may indicate the following problems:</para>
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<variablelist>
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<varlistentry>
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<term><constant>-ECHILD</constant></term>
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<listitem><para>The bus connection was created in a different process, library or module instance.</para></listitem>
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</varlistentry>
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</variablelist>
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</refsect2>
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</refsect1>
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<refsect1>
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<title>History</title>
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<para><function>sd_bus_get_n_queued_read()</function> and
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<function>sd_bus_get_n_queued_write()</function> were added in version 238.</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para><simplelist type="inline">
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<member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>sd_bus_process</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>sd_bus_send</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>sd_bus_flush</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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</simplelist></para>
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</refsect1>
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</refentry>
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