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