systemd/man/sd_journal_seek_head.xml

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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">
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Copyright 2012 Lennart Poettering
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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><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>