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<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 &lt;systemd/sd-journal.h&gt;</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 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 most recent

available entry.</para>

<para><function>sd_journal_seek_monotonic_usec()</function> seeks

to the entry 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 the entry 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

entry located 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. To

verify whether the newly selected entry actually matches the

cursor, use

<citerefentry><refentrytitle>sd_journal_test_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 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>

</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 a shared library, which can

be compiled and linked to with the

<constant>libsystemd</constant> <citerefentry project='die-net'><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>