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
  15   <refentryinfo>
  16     <title>sd_journal_get_realtime_usec</title>
  17     <productname>systemd</productname>
  18
  19     <authorgroup>
  20       <author>
  21         <contrib>Developer</contrib>
  22         <firstname>Lennart</firstname>
  23         <surname>Poettering</surname>
  24         <email>lennart@poettering.net</email>
  25       </author>
  26     </authorgroup>
  27   </refentryinfo>
  28
  29   <refmeta>
  30     <refentrytitle>sd_journal_get_realtime_usec</refentrytitle>
  31     <manvolnum>3</manvolnum>
  32   </refmeta>
  33
  34   <refnamediv>
  35     <refname>sd_journal_get_realtime_usec</refname>
  36     <refname>sd_journal_get_monotonic_usec</refname>
  37     <refpurpose>Read timestamps from the current journal entry</refpurpose>
  38   </refnamediv>
  39
  40   <refsynopsisdiv>
  41     <funcsynopsis>
  42       <funcsynopsisinfo>#include &lt;systemd/sd-journal.h&gt;</funcsynopsisinfo>
  43
  44       <funcprototype>
  45         <funcdef>int <function>sd_journal_get_realtime_usec</function></funcdef>
  46         <paramdef>sd_journal *<parameter>j</parameter></paramdef>
  47         <paramdef>uint64_t *<parameter>usec</parameter></paramdef>
  48       </funcprototype>
  49
  50       <funcprototype>
  51         <funcdef>int <function>sd_journal_get_monotonic_usec</function></funcdef>
  52         <paramdef>sd_journal *<parameter>j</parameter></paramdef>
  53         <paramdef>uint64_t *<parameter>usec</parameter></paramdef>
  54         <paramdef>sd_id128_t *<parameter>boot_id</parameter></paramdef>
  55       </funcprototype>
  56
  57     </funcsynopsis>
  58   </refsynopsisdiv>
  59
  60   <refsect1>
  61     <title>Description</title>
  62
  63     <para><function>sd_journal_get_realtime_usec()</function> gets the
  64     realtime (wallclock) timestamp of the current journal entry. It
  65     takes two arguments: the journal context object and a pointer to a
  66     64-bit unsigned integer to store the timestamp in. The timestamp
  67     is in microseconds since the epoch, i.e.
  68     <constant>CLOCK_REALTIME</constant>.</para>
  69
  70     <para><function>sd_journal_get_monotonic_usec()</function> gets
  71     the monotonic timestamp of the current journal entry. It takes
  72     three arguments: the journal context object, a pointer to a 64-bit
  73     unsigned integer to store the timestamp in, as well as a 128-bit
  74     ID buffer to store the boot ID of the monotonic timestamp. The
  75     timestamp is in microseconds since boot-up of the specific boot,
  76     i.e. <constant>CLOCK_MONOTONIC</constant>. Since the monotonic
  77     clock begins new with every reboot, it only defines a well-defined
  78     point in time when used together with an identifier identifying
  79     the boot. See
  80     <citerefentry><refentrytitle>sd_id128_get_boot</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  81     for more information. If the boot ID parameter is passed
  82     <constant>NULL</constant>, the function will fail if the monotonic
  83     timestamp of the current entry is not of the current system
  84     boot.</para>
  85
  86     <para>Note that these functions will not work before
  87     <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  88     (or related call) has been called at least
  89     once, in order to position the read pointer at a valid entry.</para>
  90   </refsect1>
  91
  92   <refsect1>
  93     <title>Return Value</title>
  94
  95     <para><function>sd_journal_get_realtime_usec()</function> and
  96     <function>sd_journal_get_monotonic_usec()</function> returns 0 on
  97     success or a negative errno-style error code. If the boot ID
  98     parameter was passed <constant>NULL</constant> and the monotonic
  99     timestamp of the current journal entry is not of the current
 100     system boot, <constant>-ESTALE</constant> is returned by
 101     <function>sd_journal_get_monotonic_usec()</function>.</para>
 102   </refsect1>
 103
 104   <refsect1>
 105     <title>Notes</title>
 106
 107     <para>The <function>sd_journal_get_realtime_usec()</function> and
 108     <function>sd_journal_get_monotonic_usec()</function> interfaces
 109     are available as a shared library, which can be compiled and
 110     linked to with the
 111     <constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 112     file.</para>
 113   </refsect1>
 114
 115   <refsect1>
 116     <title>See Also</title>
 117
 118     <para>
 119       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 120       <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 121       <citerefentry><refentrytitle>sd_journal_open</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 122       <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 123       <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 124       <citerefentry><refentrytitle>sd_id128_get_boot</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 125       <citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
 126       <citerefentry><refentrytitle>sd_journal_get_cutoff_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 127     </para>
 128   </refsect1>
 129
 130 </refentry>