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