man/sd_journal_get_realtime_usec.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4
   5 <!--
   6   SPDX-License-Identifier: LGPL-2.1+
   7
   8   This file is part of systemd.
   9
  10   Copyright 2012 Lennart Poettering
  11 -->
  12
  13 <refentry id="sd_journal_get_realtime_usec"
  14           xmlns:xi="http://www.w3.org/2001/XInclude">
  15
  16   <refentryinfo>
  17     <title>sd_journal_get_realtime_usec</title>
  18     <productname>systemd</productname>
  19
  20     <authorgroup>
  21       <author>
  22         <contrib>Developer</contrib>
  23         <firstname>Lennart</firstname>
  24         <surname>Poettering</surname>
  25         <email>lennart@poettering.net</email>
  26       </author>
  27     </authorgroup>
  28   </refentryinfo>
  29
  30   <refmeta>
  31     <refentrytitle>sd_journal_get_realtime_usec</refentrytitle>
  32     <manvolnum>3</manvolnum>
  33   </refmeta>
  34
  35   <refnamediv>
  36     <refname>sd_journal_get_realtime_usec</refname>
  37     <refname>sd_journal_get_monotonic_usec</refname>
  38     <refpurpose>Read timestamps from the current journal entry</refpurpose>
  39   </refnamediv>
  40
  41   <refsynopsisdiv>
  42     <funcsynopsis>
  43       <funcsynopsisinfo>#include &lt;systemd/sd-journal.h&gt;</funcsynopsisinfo>
  44
  45       <funcprototype>
  46         <funcdef>int <function>sd_journal_get_realtime_usec</function></funcdef>
  47         <paramdef>sd_journal *<parameter>j</parameter></paramdef>
  48         <paramdef>uint64_t *<parameter>usec</parameter></paramdef>
  49       </funcprototype>
  50
  51       <funcprototype>
  52         <funcdef>int <function>sd_journal_get_monotonic_usec</function></funcdef>
  53         <paramdef>sd_journal *<parameter>j</parameter></paramdef>
  54         <paramdef>uint64_t *<parameter>usec</parameter></paramdef>
  55         <paramdef>sd_id128_t *<parameter>boot_id</parameter></paramdef>
  56       </funcprototype>
  57
  58     </funcsynopsis>
  59   </refsynopsisdiv>
  60
  61   <refsect1>
  62     <title>Description</title>
  63
  64     <para><function>sd_journal_get_realtime_usec()</function> gets the
  65     realtime (wallclock) timestamp of the current journal entry. It
  66     takes two arguments: the journal context object and a pointer to a
  67     64-bit unsigned integer to store the timestamp in. The timestamp
  68     is in microseconds since the epoch, i.e.
  69     <constant>CLOCK_REALTIME</constant>.</para>
  70
  71     <para><function>sd_journal_get_monotonic_usec()</function> gets
  72     the monotonic timestamp of the current journal entry. It takes
  73     three arguments: the journal context object, a pointer to a 64-bit
  74     unsigned integer to store the timestamp in, as well as a 128-bit
  75     ID buffer to store the boot ID of the monotonic timestamp. The
  76     timestamp is in microseconds since boot-up of the specific boot,
  77     i.e. <constant>CLOCK_MONOTONIC</constant>. Since the monotonic
  78     clock begins new with every reboot, it only defines a well-defined
  79     point in time when used together with an identifier identifying
  80     the boot. See
  81     <citerefentry><refentrytitle>sd_id128_get_boot</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  82     for more information. If the boot ID parameter is passed
  83     <constant>NULL</constant>, the function will fail if the monotonic
  84     timestamp of the current entry is not of the current system
  85     boot.</para>
  86
  87     <para>Note that these functions will not work before
  88     <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  89     (or related call) has been called at least
  90     once, in order to position the read pointer at a valid entry.</para>
  91   </refsect1>
  92
  93   <refsect1>
  94     <title>Return Value</title>
  95
  96     <para><function>sd_journal_get_realtime_usec()</function> and
  97     <function>sd_journal_get_monotonic_usec()</function> returns 0 on
  98     success or a negative errno-style error code. If the boot ID
  99     parameter was passed <constant>NULL</constant> and the monotonic
 100     timestamp of the current journal entry is not of the current
 101     system boot, <constant>-ESTALE</constant> is returned by
 102     <function>sd_journal_get_monotonic_usec()</function>.</para>
 103   </refsect1>
 104
 105   <xi:include href="libsystemd-pkgconfig.xml" />
 106
 107   <refsect1>
 108     <title>See Also</title>
 109
 110     <para>
 111       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 112       <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 113       <citerefentry><refentrytitle>sd_journal_open</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 114       <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 115       <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 116       <citerefentry><refentrytitle>sd_id128_get_boot</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 117       <citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
 118       <citerefentry><refentrytitle>sd_journal_get_cutoff_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 119     </para>
 120   </refsect1>
 121
 122 </refentry>