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<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
This file is part of systemd.
Copyright 2012 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->
<refentry id="sd_journal_seek_head">
<refentryinfo>
<title>sd_journal_seek_head</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>Developer</contrib>
<firstname>Lennart</firstname>
<surname>Poettering</surname>
<email>lennart@poettering.net</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>sd_journal_seek_head</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>sd_journal_seek_head</refname>
<refname>sd_journal_seek_tail</refname>
<refname>sd_journal_seek_monotonic_usec</refname>
<refname>sd_journal_seek_realtime_usec</refname>
<refname>sd_journal_seek_cursor</refname>
<refpurpose>Seek to a position in the
journal</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo>
<funcprototype>
<funcdef>int <function>sd_journal_seek_head</function></funcdef>
<paramdef>sd_journal* <parameter>j</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_journal_seek_tail</function></funcdef>
<paramdef>sd_journal* <parameter>j</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_journal_seek_monotonic_usec</function></funcdef>
<paramdef>sd_journal* <parameter>j</parameter></paramdef>
<paramdef>sd_id128_t <parameter>boot_id</parameter></paramdef>
<paramdef>uint64_t <parameter>usec</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_journal_seek_realtime_usec</function></funcdef>
<paramdef>sd_journal* <parameter>j</parameter></paramdef>
<paramdef>uint64_t <parameter>usec</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_journal_seek_cursor</function></funcdef>
<paramdef>sd_journal* <parameter>j</parameter></paramdef>
<paramdef>const char * <parameter>cursor</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><function>sd_journal_seek_head()</function>
seeks to the beginning of the journal, i.e. the oldest
avilable entry.</para>
<para>Similar,
<function>sd_journal_seek_tail()</function> may be
used to seek to the end of the journal, i.e. the most
recent available entry.</para>
<para><function>sd_journal_seek_monotonic_usec()</function>
seeks to the entry with the specified monotonic
timestamp, i.e. CLOCK_MONOOTONIC. Since monotonic time
restarts on every reboot a boot ID needs to be
specified as well.</para>
<para><function>sd_journal_seek_realtime_usec()</function>
seeks to the entry with the specified realtime
(wallclock) timestamp, i.e. CLOCK_REALTIME. Note that
the realtime clock is not necessary monotonic. If a
realtime timestamp is ambiguous it is not defined
which position is seeked to.</para>
<para><function>sd_journal_seek_cursor()</function>
seeks to the entry located at the specified cursor
string. For details on cursors see
<citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
<para>Note that these calls do not actually make any
entry the new current entry, this needs to be done in
a separate step with a subsequent
<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
invocation (or a similar call). Only then entry data
may be retrieved via
<citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If
no entry exists that matches exactly the specified
seek address the next closest is seeked to. If
<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
is used the closest following entry will be seeked to,
if
<citerefentry><refentrytitle>sd_journal_previous</refentrytitle><manvolnum>3</manvolnum></citerefentry>
is used the closest preceeding entry is seeked
to.</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para>The functions return 0 on success or a negative
errno-style error code.</para>
</refsect1>
<refsect1>
<title>Notes</title>
<para>The <function>sd_journal_seek_head()</function>,
<function>sd_journal_seek_tail()</function>,
<function>sd_journal_seek_monotonic_usec()</function>,
<function>sd_journal_seek_realtime_usec()</function>,
and <function>sd_journal_seek_cursor()</function>
interfaces are available as shared library, which can
be compiled and linked to with the
<literal>libsystemd-journal</literal>
<citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
file.</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_journal_open</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_journal_get_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
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