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">
6 This file is part of systemd.
8 Copyright 2012 Lennart Poettering
10 systemd is free software; you can redistribute it and/or modify it
11 under the terms of the GNU Lesser General Public License as published by
12 the Free Software Foundation; either version 2.1 of the License, or
13 (at your option) any later version.
15 systemd is distributed in the hope that it will be useful, but
16 WITHOUT ANY WARRANTY; without even the implied warranty of
17 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
18 Lesser General Public License for more details.
20 You should have received a copy of the GNU Lesser General Public License
21 along with systemd; If not, see <http://www.gnu.org/licenses/>.
24 <refentry id="sd_journal_seek_head">
27 <title>sd_journal_seek_head</title>
28 <productname>systemd</productname>
32 <contrib>Developer</contrib>
33 <firstname>Lennart</firstname>
34 <surname>Poettering</surname>
35 <email>lennart@poettering.net</email>
41 <refentrytitle>sd_journal_seek_head</refentrytitle>
42 <manvolnum>3</manvolnum>
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
57 <funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo>
60 <funcdef>int <function>sd_journal_seek_head</function></funcdef>
61 <paramdef>sd_journal *<parameter>j</parameter></paramdef>
65 <funcdef>int <function>sd_journal_seek_tail</function></funcdef>
66 <paramdef>sd_journal *<parameter>j</parameter></paramdef>
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>
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>
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>
91 <title>Description</title>
93 <para><function>sd_journal_seek_head()</function> seeks to the
94 beginning of the journal, i.e. the oldest available entry.</para>
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>
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
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>
112 <para><function>sd_journal_seek_cursor()</function> seeks to the
113 entry located at the specified cursor string. For details on
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
120 <citerefentry><refentrytitle>sd_journal_test_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
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
125 <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
126 invocation (or a similar call). Only then, entry data may be
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>
138 <title>Return Value</title>
140 <para>The functions return 0 on success or a negative errno-style
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>
159 <title>See Also</title>
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>