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">
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   8   Copyright 2012 Lennart Poettering
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  23
  24 <refentry id="sd_journal_get_realtime_usec">
  25
  26         <refentryinfo>
  27                 <title>sd_journal_get_realtime_usec</title>
  28                 <productname>systemd</productname>
  29
  30                 <authorgroup>
  31                         <author>
  32                                 <contrib>Developer</contrib>
  33                                 <firstname>Lennart</firstname>
  34                                 <surname>Poettering</surname>
  35                                 <email>lennart@poettering.net</email>
  36                         </author>
  37                 </authorgroup>
  38         </refentryinfo>
  39
  40         <refmeta>
  41                 <refentrytitle>sd_journal_get_realtime_usec</refentrytitle>
  42                 <manvolnum>3</manvolnum>
  43         </refmeta>
  44
  45         <refnamediv>
  46                 <refname>sd_journal_get_realtime_usec</refname>
  47                 <refname>sd_journal_get_monotonic_usec</refname>
  48                 <refpurpose>Read timestamps from the current journal entry</refpurpose>
  49         </refnamediv>
  50
  51         <refsynopsisdiv>
  52                 <funcsynopsis>
  53                         <funcsynopsisinfo>#include &lt;systemd/sd-journal.h&gt;</funcsynopsisinfo>
  54
  55                         <funcprototype>
  56                                 <funcdef>int <function>sd_journal_get_realtime_usec</function></funcdef>
  57                                 <paramdef>sd_journal* <parameter>j</parameter></paramdef>
  58                                 <paramdef>uint64_t* <parameter>usec</parameter></paramdef>
  59                         </funcprototype>
  60
  61                         <funcprototype>
  62                                 <funcdef>int <function>sd_journal_get_monotonic_usec</function></funcdef>
  63                                 <paramdef>sd_journal* <parameter>j</parameter></paramdef>
  64                                 <paramdef>uint64_t* <parameter>usec</parameter></paramdef>
  65                                 <paramdef>sd_id128_t* <parameter>boot_id</parameter></paramdef>
  66                         </funcprototype>
  67
  68                 </funcsynopsis>
  69         </refsynopsisdiv>
  70
  71         <refsect1>
  72                 <title>Description</title>
  73
  74                 <para><function>sd_journal_get_realtime_usec()</function>
  75                 gets the realtime (wallclock) timestamp of the
  76                 current journal entry. It takes two arguments: the
  77                 journal context object and a pointer to a 64-bit
  78                 unsigned integer to store the timestamp in. The
  79                 timestamp is in microseconds since the epoch,
  80                 i.e. <constant>CLOCK_REALTIME</constant>.</para>
  81
  82                 <para><function>sd_journal_get_monotonic_usec()</function>
  83                 gets the monotonic timestamp of the current journal
  84                 entry. It takes three arguments: the journal context
  85                 object, a pointer to a 64-bit unsigned integer to
  86                 store the timestamp in, as well as a 128-bit ID buffer
  87                 to store the boot ID of the monotonic timestamp.
  88                 The timestamp is in microseconds since boot-up of
  89                 the specific boot,
  90                 i.e. <constant>CLOCK_MONOTONIC</constant>. Since the
  91                 monotonic clock begins new with every reboot, it only
  92                 defines a well-defined point in time when used
  93                 together with an identifier identifying the boot. See
  94                 <citerefentry><refentrytitle>sd_id128_get_boot</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  95                 for more information. If the boot ID parameter is
  96                 passed <constant>NULL</constant>, the function will
  97                 fail if the monotonic timestamp of the current entry
  98                 is not of the current system boot.</para>
  99
 100                 <para>Note that these functions will not work before
 101                 <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 102                 (or related call) has been called at least
 103                 once, in order to position the read pointer at a valid entry.</para>
 104         </refsect1>
 105
 106         <refsect1>
 107                 <title>Return Value</title>
 108
 109                 <para><function>sd_journal_get_realtime_usec()</function>
 110                 and
 111                 <function>sd_journal_get_monotonic_usec()</function>
 112                 returns 0 on success or a negative errno-style error
 113                 code. If the boot ID parameter was passed <constant>NULL</constant> and the
 114                 monotonic timestamp of the current journal entry is
 115                 not of the current system boot, -ESTALE is returned by <function>sd_journal_get_monotonic_usec()</function>.</para>
 116         </refsect1>
 117
 118         <refsect1>
 119                 <title>Notes</title>
 120
 121                 <para>The
 122                 <function>sd_journal_get_realtime_usec()</function>
 123                 and
 124                 <function>sd_journal_get_monotonic_usec()</function>
 125                 interfaces are available as shared library, which can
 126                 be compiled and linked to with the
 127                 <constant>libsystemd-journal</constant> <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 128                 file.</para>
 129         </refsect1>
 130
 131         <refsect1>
 132                 <title>See Also</title>
 133
 134                 <para>
 135                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 136                         <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 137                         <citerefentry><refentrytitle>sd_journal_open</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 138                         <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 139                         <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 140                         <citerefentry><refentrytitle>sd_id128_get_boot</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 141                         <citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
 142                         <citerefentry><refentrytitle>sd_journal_get_cutoff_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 143                 </para>
 144         </refsect1>
 145
 146 </refentry>