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https://github.com/systemd/systemd-stable.git
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0c69794138
These lines are generally out-of-date, incomplete and unnecessary. With SPDX and git repository much more accurate and fine grained information about licensing and authorship is available, hence let's drop the per-file copyright notice. Of course, removing copyright lines of others is problematic, hence this commit only removes my own lines and leaves all others untouched. It might be nicer if sooner or later those could go away too, making git the only and accurate source of authorship information.
157 lines
6.0 KiB
XML
157 lines
6.0 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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SPDX-License-Identifier: LGPL-2.1+
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-->
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<refentry id="sd_bus_message_get_monotonic_usec"
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xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>sd_bus_message_get_monotonic_usec</title>
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<productname>systemd</productname>
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<authorgroup>
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<author>
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<contrib>Developer</contrib>
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<firstname>Lennart</firstname>
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<surname>Poettering</surname>
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<email>lennart@poettering.net</email>
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</author>
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</authorgroup>
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</refentryinfo>
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<refmeta>
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<refentrytitle>sd_bus_message_get_monotonic_usec</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_message_get_monotonic_usec</refname>
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<refname>sd_bus_message_get_realtime_usec</refname>
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<refname>sd_bus_message_get_seqnum</refname>
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<refpurpose>Retrieve the sender timestamps and sequence number of a message</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_message_get_monotonic_usec</function></funcdef>
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<paramdef>sd_bus_message *<parameter>message</parameter></paramdef>
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<paramdef>uint64_t *<parameter>usec</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_bus_message_get_realtime_usec</function></funcdef>
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<paramdef>sd_bus_message *<parameter>message</parameter></paramdef>
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<paramdef>uint64_t *<parameter>usec</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_bus_message_get_seqnum</function></funcdef>
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<paramdef>sd_bus_message *<parameter>message</parameter></paramdef>
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<paramdef>uint64_t *<parameter>seqnum</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><function>sd_bus_message_get_monotonic_usec()</function>
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returns the monotonic timestamp of the time the message was sent.
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This value is in microseconds since the
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<constant>CLOCK_MONOTONIC</constant> epoch, see
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<citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>
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for details.</para>
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<para>Similarly,
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<function>sd_bus_message_get_realtime_usec()</function> returns
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the realtime (wallclock) timestamp of the time the message was
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sent. This value is in microseconds since Jan 1st, 1970, i.e. in
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the <constant>CLOCK_REALTIME</constant> clock.</para>
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<para><function>sd_bus_message_get_seqnum()</function> returns the
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kernel-assigned sequence number of the message. The kernel assigns
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a global, monotonically increasing sequence number to all messages
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transmitted on the local system, at the time the message was sent.
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This sequence number is useful for determining message send order,
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even across different buses of the local system. The sequence
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number combined with the boot ID of the system (as returned by
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<citerefentry><refentrytitle>sd_id128_get_boot</refentrytitle><manvolnum>3</manvolnum></citerefentry>)
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is a suitable globally unique identifier for bus messages.</para>
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<para>Note that the sending order and receiving order of messages
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might differ, in particular for broadcast messages. This means
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that the sequence number and the timestamps of messages a client
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reads are not necessarily monotonically increasing.</para>
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<para>These timestamps and the sequence number are attached to
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each message by the kernel and cannot be manipulated by the
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sender.</para>
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<para>Note that these timestamps are only available on some bus
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transports, and only after support for them has been negotiated
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with the
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<citerefentry><refentrytitle>sd_bus_negotiate_timestamp</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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call.</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 calls return 0 or a positive integer. On
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failure, these calls return a negative errno-style error
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code.</para>
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<para>On success, the timestamp or sequence number is returned in
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the specified 64-bit unsigned integer variable.</para>
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</refsect1>
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<refsect1>
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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>-EINVAL</constant></term>
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<listitem><para>A specified parameter is
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invalid.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-ENODATA</constant></term>
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<listitem><para>No timestamp or sequence number information is
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attached to the passed message. This error is returned if the
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underlying transport does not support timestamping or
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assigning of sequence numbers, or if this feature has not been
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negotiated with
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<citerefentry><refentrytitle>sd_bus_negotiate_timestamp</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<xi:include href="libsystemd-pkgconfig.xml" />
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_negotiate_timestamp</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_id128_get_boot</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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