systemd/man/sd_journal_seek_head.xml
Zbigniew Jędrzejewski-Szmek 11a1589223 tree-wide: drop license boilerplate
Files which are installed as-is (any .service and other unit files, .conf
files, .policy files, etc), are left as is. My assumption is that SPDX
identifiers are not yet that well known, so it's better to retain the
extended header to avoid any doubt.

I also kept any copyright lines. We can probably remove them, but it'd nice to
obtain explicit acks from all involved authors before doing that.
2018-04-06 18:58:55 +02:00

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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">
<!--
SPDX-License-Identifier: LGPL-2.1+
This file is part of systemd.
Copyright 2012 Lennart Poettering
-->
<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>All functions listed here are thread-agnostic and only a single thread may operate
on a given <structname>sd_journal</structname> object.</para>
<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>