man/sd_journal_get_realtime_usec.xml

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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> gets the
  75     realtime (wallclock) timestamp of the current journal entry. It
  76     takes two arguments: the journal context object and a pointer to a
  77     64-bit unsigned integer to store the timestamp in. The timestamp
  78     is in microseconds since the epoch, i.e.
  79     <constant>CLOCK_REALTIME</constant>.</para>
  80
  81     <para><function>sd_journal_get_monotonic_usec()</function> gets
  82     the monotonic timestamp of the current journal entry. It takes
  83     three arguments: the journal context object, a pointer to a 64-bit
  84     unsigned integer to store the timestamp in, as well as a 128-bit
  85     ID buffer to store the boot ID of the monotonic timestamp. The
  86     timestamp is in microseconds since boot-up of the specific boot,
  87     i.e. <constant>CLOCK_MONOTONIC</constant>. Since the monotonic
  88     clock begins new with every reboot, it only defines a well-defined
  89     point in time when used together with an identifier identifying
  90     the boot. See
  91     <citerefentry><refentrytitle>sd_id128_get_boot</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  92     for more information. If the boot ID parameter is passed
  93     <constant>NULL</constant>, the function will fail if the monotonic
  94     timestamp of the current entry is not of the current system
  95     boot.</para>
  96
  97     <para>Note that these functions will not work before
  98     <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  99     (or related call) has been called at least
 100     once, in order to position the read pointer at a valid entry.</para>
 101   </refsect1>
 102
 103   <refsect1>
 104     <title>Return Value</title>
 105
 106     <para><function>sd_journal_get_realtime_usec()</function> and
 107     <function>sd_journal_get_monotonic_usec()</function> returns 0 on
 108     success or a negative errno-style error code. If the boot ID
 109     parameter was passed <constant>NULL</constant> and the monotonic
 110     timestamp of the current journal entry is not of the current
 111     system boot, <constant>-ESTALE</constant> is returned by
 112     <function>sd_journal_get_monotonic_usec()</function>.</para>
 113   </refsect1>
 114
 115   <refsect1>
 116     <title>Notes</title>
 117
 118     <para>The <function>sd_journal_get_realtime_usec()</function> and
 119     <function>sd_journal_get_monotonic_usec()</function> interfaces
 120     are available as a shared library, which can be compiled and
 121     linked to with the
 122     <constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 123     file.</para>
 124   </refsect1>
 125
 126   <refsect1>
 127     <title>See Also</title>
 128
 129     <para>
 130       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 131       <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 132       <citerefentry><refentrytitle>sd_journal_open</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 133       <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 134       <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 135       <citerefentry><refentrytitle>sd_id128_get_boot</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 136       <citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
 137       <citerefentry><refentrytitle>sd_journal_get_cutoff_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 138     </para>
 139   </refsect1>
 140
 141 </refentry>