man/sd_journal_seek_head.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
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   8   Copyright 2012 Lennart Poettering
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  23
  24 <refentry id="sd_journal_seek_head">
  25
  26   <refentryinfo>
  27     <title>sd_journal_seek_head</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_seek_head</refentrytitle>
  42     <manvolnum>3</manvolnum>
  43   </refmeta>
  44
  45   <refnamediv>
  46     <refname>sd_journal_seek_head</refname>
  47     <refname>sd_journal_seek_tail</refname>
  48     <refname>sd_journal_seek_monotonic_usec</refname>
  49     <refname>sd_journal_seek_realtime_usec</refname>
  50     <refname>sd_journal_seek_cursor</refname>
  51     <refpurpose>Seek to a position in the
  52     journal</refpurpose>
  53   </refnamediv>
  54
  55   <refsynopsisdiv>
  56     <funcsynopsis>
  57       <funcsynopsisinfo>#include &lt;systemd/sd-journal.h&gt;</funcsynopsisinfo>
  58
  59       <funcprototype>
  60         <funcdef>int <function>sd_journal_seek_head</function></funcdef>
  61         <paramdef>sd_journal *<parameter>j</parameter></paramdef>
  62       </funcprototype>
  63
  64       <funcprototype>
  65         <funcdef>int <function>sd_journal_seek_tail</function></funcdef>
  66         <paramdef>sd_journal *<parameter>j</parameter></paramdef>
  67       </funcprototype>
  68
  69       <funcprototype>
  70         <funcdef>int <function>sd_journal_seek_monotonic_usec</function></funcdef>
  71         <paramdef>sd_journal *<parameter>j</parameter></paramdef>
  72         <paramdef>sd_id128_t <parameter>boot_id</parameter></paramdef>
  73         <paramdef>uint64_t <parameter>usec</parameter></paramdef>
  74       </funcprototype>
  75
  76       <funcprototype>
  77         <funcdef>int <function>sd_journal_seek_realtime_usec</function></funcdef>
  78         <paramdef>sd_journal *<parameter>j</parameter></paramdef>
  79         <paramdef>uint64_t <parameter>usec</parameter></paramdef>
  80       </funcprototype>
  81
  82       <funcprototype>
  83         <funcdef>int <function>sd_journal_seek_cursor</function></funcdef>
  84         <paramdef>sd_journal *<parameter>j</parameter></paramdef>
  85         <paramdef>const char *<parameter>cursor</parameter></paramdef>
  86       </funcprototype>
  87     </funcsynopsis>
  88   </refsynopsisdiv>
  89
  90   <refsect1>
  91     <title>Description</title>
  92
  93     <para><function>sd_journal_seek_head()</function> seeks to the
  94     beginning of the journal, i.e. the oldest available entry.</para>
  95
  96     <para>Similarly, <function>sd_journal_seek_tail()</function> may
  97     be used to seek to the end of the journal, i.e. the most recent
  98     available entry.</para>
  99
 100     <para><function>sd_journal_seek_monotonic_usec()</function> seeks
 101     to the entry with the specified monotonic timestamp, i.e.
 102     <constant>CLOCK_MONOTONIC</constant>. Since monotonic time
 103     restarts on every reboot a boot ID needs to be specified as
 104     well.</para>
 105
 106     <para><function>sd_journal_seek_realtime_usec()</function> seeks
 107     to the entry with the specified realtime (wallclock) timestamp,
 108     i.e. <constant>CLOCK_REALTIME</constant>. Note that the realtime
 109     clock is not necessarily monotonic. If a realtime timestamp is
 110     ambiguous, it is not defined which position is sought to.</para>
 111
 112     <para><function>sd_journal_seek_cursor()</function> seeks to the
 113     entry located at the specified cursor string. For details on
 114     cursors, see
 115     <citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 116     If no entry matching the specified cursor is found the call will
 117     seek to the next closest entry (in terms of time) instead. To
 118     verify whether the newly selected entry actually matches the
 119     cursor, use
 120     <citerefentry><refentrytitle>sd_journal_test_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
 121
 122     <para>Note that these calls do not actually make any entry the new
 123     current entry, this needs to be done in a separate step with a
 124     subsequent
 125     <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 126     invocation (or a similar call). Only then, entry data may be
 127     retrieved via
 128     <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 129     If no entry exists that matches exactly the specified seek
 130     address, the next closest is sought to. If
 131     <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 132     is used, the closest following entry will be sought to, if
 133     <citerefentry><refentrytitle>sd_journal_previous</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 134     is used the closest preceding entry is sought to.</para>
 135   </refsect1>
 136
 137   <refsect1>
 138     <title>Return Value</title>
 139
 140     <para>The functions return 0 on success or a negative errno-style
 141     error code.</para>
 142   </refsect1>
 143
 144   <refsect1>
 145     <title>Notes</title>
 146
 147     <para>The <function>sd_journal_seek_head()</function>,
 148     <function>sd_journal_seek_tail()</function>,
 149     <function>sd_journal_seek_monotonic_usec()</function>,
 150     <function>sd_journal_seek_realtime_usec()</function>,
 151     and <function>sd_journal_seek_cursor()</function>
 152     interfaces are available as a shared library, which can
 153     be compiled and linked to with the
 154     <constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 155     file.</para>
 156   </refsect1>
 157
 158   <refsect1>
 159     <title>See Also</title>
 160
 161     <para>
 162       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 163       <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 164       <citerefentry><refentrytitle>sd_journal_open</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 165       <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 166       <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 167       <citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 168       <citerefentry><refentrytitle>sd_journal_get_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 169     </para>
 170   </refsect1>
 171
 172 </refentry>