147 lines
7.1 KiB
XML
147 lines
7.1 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 2012 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_journal_get_realtime_usec">
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<refentryinfo>
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<title>sd_journal_get_realtime_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_journal_get_realtime_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_journal_get_realtime_usec</refname>
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<refname>sd_journal_get_monotonic_usec</refname>
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<refpurpose>Read timestamps from the current journal entry</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo>
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<funcprototype>
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<funcdef>int <function>sd_journal_get_realtime_usec</function></funcdef>
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<paramdef>sd_journal* <parameter>j</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_journal_get_monotonic_usec</function></funcdef>
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<paramdef>sd_journal* <parameter>j</parameter></paramdef>
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<paramdef>uint64_t* <parameter>usec</parameter></paramdef>
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<paramdef>sd_id128_t* <parameter>boot_id</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_journal_get_realtime_usec()</function>
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gets the realtime (wallclock) timestamp of the
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current journal entry. It takes two arguments: the
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journal context object and a pointer to a 64-bit
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unsigned integer to store the timestamp in. The
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timestamp is in microseconds since the epoch,
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i.e. <constant>CLOCK_REALTIME</constant>.</para>
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<para><function>sd_journal_get_monotonic_usec()</function>
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gets the monotonic timestamp of the current journal
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entry. It takes three arguments: the journal context
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object, a pointer to a 64-bit unsigned integer to
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store the timestamp in, as well as a 128-bit ID buffer
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to store the boot ID of the monotonic timestamp.
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The timestamp is in microseconds since boot-up of
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the specific boot,
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i.e. <constant>CLOCK_MONOTONIC</constant>. Since the
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monotonic clock begins new with every reboot, it only
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defines a well-defined point in time when used
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together with an identifier identifying the boot. See
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<citerefentry><refentrytitle>sd_id128_get_boot</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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for more information. If the boot ID parameter is
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passed <constant>NULL</constant>, the function will
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fail if the monotonic timestamp of the current entry
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is not of the current system boot.</para>
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<para>Note that these functions will not work before
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<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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(or related call) has been called at least
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once, in order to position the read pointer at a valid entry.</para>
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</refsect1>
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<refsect1>
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<title>Return Value</title>
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<para><function>sd_journal_get_realtime_usec()</function>
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and
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<function>sd_journal_get_monotonic_usec()</function>
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returns 0 on success or a negative errno-style error
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code. If the boot ID parameter was passed <constant>NULL</constant> and the
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monotonic timestamp of the current journal entry is
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not of the current system boot, -ESTALE is returned by <function>sd_journal_get_monotonic_usec()</function>.</para>
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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_journal_get_realtime_usec()</function>
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and
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<function>sd_journal_get_monotonic_usec()</function>
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interfaces are available as a shared library, which can
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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-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_journal_open</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_id128_get_boot</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_journal_get_cutoff_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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