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. CLOCK_REALTIME.</para>
  81
  82                 <para><function>sd_journal_get_monotonic_usec()</function>
  83                 gets the monotonic timestamp of the current
  84                 journal entry.  It takes three arguments: the journal
  85                 context object, a pointer to a 64 Bit unsigned integer
  86                 to store the timestamp in as well as a 128 Bit ID
  87                 buffer to store the boot ID of the monotonic timestamp
  88                 in. The timestamp is in microseconds since boot-up of
  89                 the specific boot, i.e. CLOCK_MONOTONIC. Since the
  90                 monotonic clock begins new with every reboot it only
  91                 defines a well-defined point in time when used
  92                 together with an identifier identifying the boot, see
  93                 <citerefentry><refentrytitle>sd_id128_get_boot</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  94                 for more information. If the boot ID parameter is
  95                 passed NULL the function will fail if the monotonic
  96                 timestamp of the current entry is not of the current
  97                 system boot.</para>
  98
  99                 <para>Note that these functions will not work before
 100                 <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 101                 (or related call) has been called at least
 102                 once, in order to position the read pointer at a valid entry.</para>
 103         </refsect1>
 104
 105         <refsect1>
 106                 <title>Return Value</title>
 107
 108                 <para><function>sd_journal_get_realtime_usec()</function>
 109                 and
 110                 <function>sd_journal_get_monotonic_usec()</function>
 111                 returns 0 on success or a negative errno-style error
 112                 code. If the boot ID parameter was passed NULL and the
 113                 monotonic timestamp of the current journal entry is
 114                 not of the current system boot, -ESTALE is returned by <function>sd_journal_get_monotonic_usec()</function>.</para>
 115         </refsect1>
 116
 117         <refsect1>
 118                 <title>Notes</title>
 119
 120                 <para>The
 121                 <function>sd_journal_get_realtime_usec()</function>
 122                 and
 123                 <function>sd_journal_get_monotonic_usec()</function>
 124                 interfaces are available as shared library, which can
 125                 be compiled and linked to with the
 126                 <literal>libsystemd-journal</literal>
 127                 <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>