[thirdparty/systemd.git] / man / sd_journal_seek_head.xml

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<!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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<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>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_MONOTONIC. 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 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 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>
Commit	Line	Data
639a6a25 LP	1	<?xml version='1.0'?> <!---nxml--->
	2	<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
	3	"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
	4
	5	<!--
	6	This file is part of systemd.
	7
	8	Copyright 2012 Lennart Poettering
	9
	10	systemd is free software; you can redistribute it and/or modify it
	11	under the terms of the GNU Lesser General Public License as published by
	12	the Free Software Foundation; either version 2.1 of the License, or
	13	(at your option) any later version.
	14
	15	systemd is distributed in the hope that it will be useful, but
	16	WITHOUT ANY WARRANTY; without even the implied warranty of
	17	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	18	Lesser General Public License for more details.
	19
	20	You should have received a copy of the GNU Lesser General Public License
	21	along with systemd; If not, see <http://www.gnu.org/licenses/>.
	22	-->
	23
	24	<refentry id="sd_journal_seek_head">
	25
	26	<refentryinfo>
	27	<title>sd_journal_seek_head</title>
	28	<productname>systemd</productname>
	29
	30	<authorgroup>
	31	<author>
	32	<contrib>Developer</contrib>
	33	<firstname>Lennart</firstname>
	34	<surname>Poettering</surname>
	35	<email>lennart@poettering.net</email>
	36	</author>
	37	</authorgroup>
	38	</refentryinfo>
	39
	40	<refmeta>
	41	<refentrytitle>sd_journal_seek_head</refentrytitle>
	42	<manvolnum>3</manvolnum>
	43	</refmeta>
	44
	45	<refnamediv>
	46	<refname>sd_journal_seek_head</refname>
	47	<refname>sd_journal_seek_tail</refname>
	48	<refname>sd_journal_seek_monotonic_usec</refname>
	49	<refname>sd_journal_seek_realtime_usec</refname>
	50	<refname>sd_journal_seek_cursor</refname>
	51	<refpurpose>Seek to a position in the
	52	journal</refpurpose>
	53	</refnamediv>
	54
	55	<refsynopsisdiv>
	56	<funcsynopsis>
	57	<funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo>
	58
	59	<funcprototype>
	60	<funcdef>int <function>sd_journal_seek_head</function></funcdef>
	61	<paramdef>sd_journal* <parameter>j</parameter></paramdef>
	62	</funcprototype>
	63
	64	<funcprototype>
65	<funcdef>int <function>sd_journal_seek_tail</function></funcdef>
66	<paramdef>sd_journal* <parameter>j</parameter></paramdef>
67	</funcprototype>
68
69	<funcprototype>
70	<funcdef>int <function>sd_journal_seek_monotonic_usec</function></funcdef>
71	<paramdef>sd_journal* <parameter>j</parameter></paramdef>
72	<paramdef>sd_id128_t <parameter>boot_id</parameter></paramdef>
73	<paramdef>uint64_t <parameter>usec</parameter></paramdef>
74	</funcprototype>
75
76	<funcprototype>
77	<funcdef>int <function>sd_journal_seek_realtime_usec</function></funcdef>
78	<paramdef>sd_journal* <parameter>j</parameter></paramdef>
79	<paramdef>uint64_t <parameter>usec</parameter></paramdef>
80	</funcprototype>
81
82	<funcprototype>
83	<funcdef>int <function>sd_journal_seek_cursor</function></funcdef>
84	<paramdef>sd_journal* <parameter>j</parameter></paramdef>
85	<paramdef>const char * <parameter>cursor</parameter></paramdef>
86	</funcprototype>
87	</funcsynopsis>
88	</refsynopsisdiv>
89
90	<refsect1>
91	<title>Description</title>
92
93	<para><function>sd_journal_seek_head()</function>
94	seeks to the beginning of the journal, i.e. the oldest
49f43d5f	95	available entry.</para>
639a6a25 LP	96
	97	<para>Similar,
	98	<function>sd_journal_seek_tail()</function> may be
	99	used to seek to the end of the journal, i.e. the most
	100	recent available entry.</para>
	101
	102	<para><function>sd_journal_seek_monotonic_usec()</function>
	103	seeks to the entry with the specified monotonic
3ef51b2c	104	timestamp, i.e. CLOCK_MONOTONIC. Since monotonic time
639a6a25 LP	105	restarts on every reboot a boot ID needs to be
	106	specified as well.</para>
	107
	108	<para><function>sd_journal_seek_realtime_usec()</function>
	109	seeks to the entry with the specified realtime
	110	(wallclock) timestamp, i.e. CLOCK_REALTIME. Note that
bb31a4ac	111	the realtime clock is not necessarily monotonic. If a
639a6a25	112	realtime timestamp is ambiguous it is not defined
49f43d5f	113	which position is sought to.</para>
639a6a25 LP	114
	115	<para><function>sd_journal_seek_cursor()</function>
	116	seeks to the entry located at the specified cursor
	117	string. For details on cursors see
c6511e85 LP	118	<citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If
	119	no entry matching the specified cursor is found the
	120	call will seek to the next closest entry (in terms of
	121	time) instead. To verify whether the newly selected
	122	entry actually matches the cursor use
	123	<citerefentry><refentrytitle>sd_journal_test_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
639a6a25 LP	124
	125	<para>Note that these calls do not actually make any
	126	entry the new current entry, this needs to be done in
	127	a separate step with a subsequent
	128	<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
	129	invocation (or a similar call). Only then entry data
	130	may be retrieved via
	131	<citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If
	132	no entry exists that matches exactly the specified
49f43d5f	133	seek address the next closest is sought to. If
639a6a25	134	<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
49f43d5f	135	is used the closest following entry will be sought to,
639a6a25 LP	136	if
639a6a25 LP	137	<citerefentry><refentrytitle>sd_journal_previous</refentrytitle><manvolnum>3</manvolnum></citerefentry>
49f43d5f	138	is used the closest preceding entry is sought
639a6a25 LP	139	to.</para>
	140	</refsect1>
	141
	142	<refsect1>
	143	<title>Return Value</title>
	144
	145	<para>The functions return 0 on success or a negative
	146	errno-style error code.</para>
	147	</refsect1>
	148
	149	<refsect1>
	150	<title>Notes</title>
	151
	152	<para>The <function>sd_journal_seek_head()</function>,
	153	<function>sd_journal_seek_tail()</function>,
	154	<function>sd_journal_seek_monotonic_usec()</function>,
	155	<function>sd_journal_seek_realtime_usec()</function>,
	156	and <function>sd_journal_seek_cursor()</function>
	157	interfaces are available as shared library, which can
	158	be compiled and linked to with the
	159	<literal>libsystemd-journal</literal>
	160	<citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
	161	file.</para>
	162	</refsect1>
	163
	164	<refsect1>
	165	<title>See Also</title>
	166
	167	<para>
	168	<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
	169	<citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
	170	<citerefentry><refentrytitle>sd_journal_open</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
	171	<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
	172	<citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
	173	<citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
	174	<citerefentry><refentrytitle>sd_journal_get_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>
	175	</para>
	176	</refsect1>
	177
	178	</refentry>