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systemd/man/sd_journal_get_realtime_usec.xml
Zbigniew Jędrzejewski-Szmek 11a1589223 tree-wide: drop license boilerplate
Files which are installed as-is (any .service and other unit files, .conf
files, .policy files, etc), are left as is. My assumption is that SPDX
identifiers are not yet that well known, so it's better to retain the
extended header to avoid any doubt.

I also kept any copyright lines. We can probably remove them, but it'd nice to
obtain explicit acks from all involved authors before doing that.
2018-04-06 18:58:55 +02:00

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<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
SPDX-License-Identifier: LGPL-2.1+
This file is part of systemd.
Copyright 2012 Lennart Poettering
-->
<refentry id="sd_journal_get_realtime_usec">
<refentryinfo>
<title>sd_journal_get_realtime_usec</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>Developer</contrib>
<firstname>Lennart</firstname>
<surname>Poettering</surname>
<email>lennart@poettering.net</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>sd_journal_get_realtime_usec</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>sd_journal_get_realtime_usec</refname>
<refname>sd_journal_get_monotonic_usec</refname>
<refpurpose>Read timestamps from the current journal entry</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include &lt;systemd/sd-journal.h&gt;</funcsynopsisinfo>
<funcprototype>
<funcdef>int <function>sd_journal_get_realtime_usec</function></funcdef>
<paramdef>sd_journal *<parameter>j</parameter></paramdef>
<paramdef>uint64_t *<parameter>usec</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_journal_get_monotonic_usec</function></funcdef>
<paramdef>sd_journal *<parameter>j</parameter></paramdef>
<paramdef>uint64_t *<parameter>usec</parameter></paramdef>
<paramdef>sd_id128_t *<parameter>boot_id</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><function>sd_journal_get_realtime_usec()</function> gets the
realtime (wallclock) timestamp of the current journal entry. It
takes two arguments: the journal context object and a pointer to a
64-bit unsigned integer to store the timestamp in. The timestamp
is in microseconds since the epoch, i.e.
<constant>CLOCK_REALTIME</constant>.</para>
<para><function>sd_journal_get_monotonic_usec()</function> gets
the monotonic timestamp of the current journal entry. It takes
three arguments: the journal context object, a pointer to a 64-bit
unsigned integer to store the timestamp in, as well as a 128-bit
ID buffer to store the boot ID of the monotonic timestamp. The
timestamp is in microseconds since boot-up of the specific boot,
i.e. <constant>CLOCK_MONOTONIC</constant>. Since the monotonic
clock begins new with every reboot, it only defines a well-defined
point in time when used together with an identifier identifying
the boot. See
<citerefentry><refentrytitle>sd_id128_get_boot</refentrytitle><manvolnum>3</manvolnum></citerefentry>
for more information. If the boot ID parameter is passed
<constant>NULL</constant>, the function will fail if the monotonic
timestamp of the current entry is not of the current system
boot.</para>
<para>Note that these functions will not work before
<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
(or related call) has been called at least
once, in order to position the read pointer at a valid entry.</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para><function>sd_journal_get_realtime_usec()</function> and
<function>sd_journal_get_monotonic_usec()</function> returns 0 on
success or a negative errno-style error code. If the boot ID
parameter was passed <constant>NULL</constant> and the monotonic
timestamp of the current journal entry is not of the current
system boot, <constant>-ESTALE</constant> is returned by
<function>sd_journal_get_monotonic_usec()</function>.</para>
</refsect1>
<refsect1>
<title>Notes</title>
<para>The <function>sd_journal_get_realtime_usec()</function> and
<function>sd_journal_get_monotonic_usec()</function> interfaces
are available as a shared library, which can be compiled and
linked to with the
<constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
file.</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_journal_open</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_id128_get_boot</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_journal_get_cutoff_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>