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5aded36978
It is annoying when we have dead links on fd.o. Add project='man-pages|die-net|archlinux' to <citerefentry>-ies. In generated html, add external links to http://man7.org/linux/man-pages/man, http://linux.die.net/man/, https://www.archlinux.org/. By default, pages in sections 2 and 4 go to man7, since Michael Kerrisk is the autorative source on kernel related stuff. The rest of links goes to linux.die.net, because they have the manpages. Except for the pacman stuff, since it seems to be only available from archlinux.org. Poor gummiboot gets no link, because gummitboot(8) ain't to be found on the net. According to common wisdom, that would mean that it does not exist. But I have seen Kay using it, so I know it does, and deserves to be found. Can somebody be nice and put it up somewhere?
191 lines
9.0 KiB
XML
191 lines
9.0 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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This file is part of systemd.
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Copyright 2013 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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-->
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<refentry id="sd_bus_message_get_monotonic_usec" conditional="ENABLE_KDBUS">
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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
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message was sent. This value is in microseconds since
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the <literal>CLOCK_MONOTONIC</literal> 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>Similar,
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<function>sd_bus_message_get_realtime_usec()</function>
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returns the realtime (wallclock) timestamp of the time
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the message was sent. This value is in microseconds
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since Jan 1st, 1970, i.e. in the
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<literal>CLOCK_REALTIME</literal> clock.</para>
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<para><function>sd_bus_message_get_seqnum()</function>
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returns the kernel-assigned sequence number of the
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message. The kernel assigns a global, monotonically
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increasing sequence number to all messages transmitted
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on the local system, at the time the message was
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sent. This sequence number is useful for determining
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message send order, even across different busses of
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the local system. The sequence number combined with
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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
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messages.</para>
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<para>Note that the sending order and receiving order
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of messages might differ, in particular for broadcast
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messages. This means that the sequence number and the
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timestamps of messages a client reads are not
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necessarily monotonically increasing.</para>
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<para>These timestamps and the sequence number are
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attached to each message by the kernel and cannot be
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manipulated by the sender.</para>
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<para>Note that these timestamps are only available on
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some bus transports, and only after support for them
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has been negotiated 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
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integer. On failure, these calls return a negative
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errno-style error code.</para>
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<para>On success, the timestamp or sequence number is
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returned in the specified 64-bit unsigned integer
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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><varname>-EINVAL</varname></term>
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<listitem><para>A specified parameter
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is invalid.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>-ENODATA</varname></term>
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<listitem><para>No timestamp or
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sequence number information is
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attached to the passed message. This
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error is returned if the underlying
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transport does not support
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timestamping or assigning of sequence
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numbers, or if this feature has not
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been 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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<refsect1>
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<title>Notes</title>
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<para>The
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<function>sd_bus_message_get_monotonic_usec()</function>,
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<function>sd_bus_message_get_realtime_usec()</function>,
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and <function>sd_bus_message_get_seqnum()</function>
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interfaces are available as a shared library, which
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can be compiled and linked to with the
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<constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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file.</para>
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</refsect1>
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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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