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>
  94                 seeks to the beginning of the journal, i.e. the oldest
  95                 available entry.</para>
  96
  97                 <para>Similar,
  98                 <function>sd_journal_seek_tail()</function> may be
  99                 used to seek to the end of the journal, i.e. the most
 100                 recent available entry.</para>
 101
 102                 <para><function>sd_journal_seek_monotonic_usec()</function>
 103                 seeks to the entry with the specified monotonic
 104                 timestamp, i.e. CLOCK_MONOOTONIC. Since monotonic time
 105                 restarts on every reboot a boot ID needs to be
 106                 specified as well.</para>
 107
 108                 <para><function>sd_journal_seek_realtime_usec()</function>
 109                 seeks to the entry with the specified realtime
 110                 (wallclock) timestamp, i.e. CLOCK_REALTIME. Note that
 111                 the realtime clock is not necessary monotonic. If a
 112                 realtime timestamp is ambiguous it is not defined
 113                 which position is sought to.</para>
 114
 115                 <para><function>sd_journal_seek_cursor()</function>
 116                 seeks to the entry located at the specified cursor
 117                 string. For details on cursors see
 118                 <citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
 119
 120                 <para>Note that these calls do not actually make any
 121                 entry the new current entry, this needs to be done in
 122                 a separate step with a subsequent
 123                 <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 124                 invocation (or a similar call). Only then entry data
 125                 may be retrieved via
 126                 <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If
 127                 no entry exists that matches exactly the specified
 128                 seek address the next closest is sought to. If
 129                 <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 130                 is used the closest following entry will be sought to,
 131                 if
 132                 <citerefentry><refentrytitle>sd_journal_previous</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 133                 is used the closest preceding entry is sought
 134                 to.</para>
 135         </refsect1>
 136
 137         <refsect1>
 138                 <title>Return Value</title>
 139
 140                 <para>The functions return 0 on success or a negative
 141                 errno-style 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 shared library, which can
 153                 be compiled and linked to with the
 154                 <literal>libsystemd-journal</literal>
 155                 <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 156                 file.</para>
 157         </refsect1>
 158
 159         <refsect1>
 160                 <title>See Also</title>
 161
 162                 <para>
 163                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 164                         <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 165                         <citerefentry><refentrytitle>sd_journal_open</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 166                         <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 167                         <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 168                         <citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 169                         <citerefentry><refentrytitle>sd_journal_get_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 170                 </para>
 171         </refsect1>
 172
 173 </refentry>