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8dc385e770
Shift the asterisks in the documentation's prototypes such that they are consistent among each other. Use the right side to match source code.
184 lines
8.6 KiB
XML
184 lines
8.6 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">
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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 increasing
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sequence number to all messages sent on the local
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system. 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>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><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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