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<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
<refentry id="sd_journal_seek_head" xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>sd_journal_seek_head</title>
<productname>systemd</productname>
</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. to the
position before the oldest available entry.</para>
<para>Similarly, <function>sd_journal_seek_tail()</function> may be used to seek to the end of the
journal, i.e. the position after the most recent available entry.</para>
<para><function>sd_journal_seek_monotonic_usec()</function> seeks to a position with the specified
monotonic timestamp, i.e. <constant>CLOCK_MONOTONIC</constant>. 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 a position with the specified
realtime (wallclock) timestamp, i.e. <constant>CLOCK_REALTIME</constant>. Note that the realtime clock is
not necessarily monotonic. If a realtime timestamp is ambiguous, it is not defined which position is
sought to.</para>
<para><function>sd_journal_seek_cursor()</function> seeks to the position at the specified cursor
string. For details on cursors, see
<citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
If no entry matching the specified cursor is found the call will seek to the next closest entry (in terms
of time) instead.</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>
or an entry cursor be retrieved via
<citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
If no entry exists that matches exactly the specified seek address, the next closest is sought to. If
<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry> is
used, the closest following entry will be sought to, if
<citerefentry><refentrytitle>sd_journal_previous</refentrytitle><manvolnum>3</manvolnum></citerefentry>
is used the closest preceding entry is sought to.</para>
<para>After the seek is done, and
<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
or a similar call has been made,
<citerefentry><refentrytitle>sd_journal_test_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>
may be used to verify whether the newly selected entry actually matches the cursor.
</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>
<xi:include href="threads-aware.xml" xpointer="strict"/>
<xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/>
</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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