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1 | <?xml version='1.0'?> <!--*-nxml-*--> |
2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" | |
12b42c76 | 3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
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4 | |
5 | <!-- | |
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6 | SPDX-License-Identifier: LGPL-2.1+ |
7 | ||
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8 | This file is part of systemd. |
9 | ||
10 | Copyright 2012 Lennart Poettering | |
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11 | --> |
12 | ||
13 | <refentry id="sd_journal_seek_head"> | |
14 | ||
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15 | <refentryinfo> |
16 | <title>sd_journal_seek_head</title> | |
17 | <productname>systemd</productname> | |
18 | ||
19 | <authorgroup> | |
20 | <author> | |
21 | <contrib>Developer</contrib> | |
22 | <firstname>Lennart</firstname> | |
23 | <surname>Poettering</surname> | |
24 | <email>lennart@poettering.net</email> | |
25 | </author> | |
26 | </authorgroup> | |
27 | </refentryinfo> | |
28 | ||
29 | <refmeta> | |
30 | <refentrytitle>sd_journal_seek_head</refentrytitle> | |
31 | <manvolnum>3</manvolnum> | |
32 | </refmeta> | |
33 | ||
34 | <refnamediv> | |
35 | <refname>sd_journal_seek_head</refname> | |
36 | <refname>sd_journal_seek_tail</refname> | |
37 | <refname>sd_journal_seek_monotonic_usec</refname> | |
38 | <refname>sd_journal_seek_realtime_usec</refname> | |
39 | <refname>sd_journal_seek_cursor</refname> | |
40 | <refpurpose>Seek to a position in the | |
41 | journal</refpurpose> | |
42 | </refnamediv> | |
43 | ||
44 | <refsynopsisdiv> | |
45 | <funcsynopsis> | |
46 | <funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo> | |
47 | ||
48 | <funcprototype> | |
49 | <funcdef>int <function>sd_journal_seek_head</function></funcdef> | |
50 | <paramdef>sd_journal *<parameter>j</parameter></paramdef> | |
51 | </funcprototype> | |
52 | ||
53 | <funcprototype> | |
54 | <funcdef>int <function>sd_journal_seek_tail</function></funcdef> | |
55 | <paramdef>sd_journal *<parameter>j</parameter></paramdef> | |
56 | </funcprototype> | |
57 | ||
58 | <funcprototype> | |
59 | <funcdef>int <function>sd_journal_seek_monotonic_usec</function></funcdef> | |
60 | <paramdef>sd_journal *<parameter>j</parameter></paramdef> | |
61 | <paramdef>sd_id128_t <parameter>boot_id</parameter></paramdef> | |
62 | <paramdef>uint64_t <parameter>usec</parameter></paramdef> | |
63 | </funcprototype> | |
64 | ||
65 | <funcprototype> | |
66 | <funcdef>int <function>sd_journal_seek_realtime_usec</function></funcdef> | |
67 | <paramdef>sd_journal *<parameter>j</parameter></paramdef> | |
68 | <paramdef>uint64_t <parameter>usec</parameter></paramdef> | |
69 | </funcprototype> | |
70 | ||
71 | <funcprototype> | |
72 | <funcdef>int <function>sd_journal_seek_cursor</function></funcdef> | |
73 | <paramdef>sd_journal *<parameter>j</parameter></paramdef> | |
74 | <paramdef>const char *<parameter>cursor</parameter></paramdef> | |
75 | </funcprototype> | |
76 | </funcsynopsis> | |
77 | </refsynopsisdiv> | |
78 | ||
79 | <refsect1> | |
80 | <title>Description</title> | |
81 | ||
82 | <para><function>sd_journal_seek_head()</function> seeks to the | |
83 | beginning of the journal, i.e. the oldest available entry.</para> | |
84 | ||
85 | <para>Similarly, <function>sd_journal_seek_tail()</function> may | |
86 | be used to seek to the end of the journal, i.e. the most recent | |
87 | available entry.</para> | |
88 | ||
89 | <para><function>sd_journal_seek_monotonic_usec()</function> seeks | |
90 | to the entry with the specified monotonic timestamp, i.e. | |
91 | <constant>CLOCK_MONOTONIC</constant>. Since monotonic time | |
92 | restarts on every reboot a boot ID needs to be specified as | |
93 | well.</para> | |
94 | ||
95 | <para><function>sd_journal_seek_realtime_usec()</function> seeks | |
96 | to the entry with the specified realtime (wallclock) timestamp, | |
97 | i.e. <constant>CLOCK_REALTIME</constant>. Note that the realtime | |
98 | clock is not necessarily monotonic. If a realtime timestamp is | |
99 | ambiguous, it is not defined which position is sought to.</para> | |
100 | ||
101 | <para><function>sd_journal_seek_cursor()</function> seeks to the | |
102 | entry located at the specified cursor string. For details on | |
103 | cursors, see | |
104 | <citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>. | |
105 | If no entry matching the specified cursor is found the call will | |
106 | seek to the next closest entry (in terms of time) instead. To | |
107 | verify whether the newly selected entry actually matches the | |
108 | cursor, use | |
109 | <citerefentry><refentrytitle>sd_journal_test_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> | |
110 | ||
111 | <para>Note that these calls do not actually make any entry the new | |
112 | current entry, this needs to be done in a separate step with a | |
113 | subsequent | |
114 | <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
115 | invocation (or a similar call). Only then, entry data may be | |
116 | retrieved via | |
117 | <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>. | |
118 | If no entry exists that matches exactly the specified seek | |
119 | address, the next closest is sought to. If | |
120 | <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
121 | is used, the closest following entry will be sought to, if | |
122 | <citerefentry><refentrytitle>sd_journal_previous</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
123 | is used the closest preceding entry is sought to.</para> | |
124 | </refsect1> | |
125 | ||
126 | <refsect1> | |
127 | <title>Return Value</title> | |
128 | ||
129 | <para>The functions return 0 on success or a negative errno-style | |
130 | error code.</para> | |
131 | </refsect1> | |
132 | ||
133 | <refsect1> | |
134 | <title>Notes</title> | |
135 | ||
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136 | <para>All functions listed here are thread-agnostic and only a single thread may operate |
137 | on a given <structname>sd_journal</structname> object.</para> | |
138 | ||
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139 | <para>The <function>sd_journal_seek_head()</function>, |
140 | <function>sd_journal_seek_tail()</function>, | |
141 | <function>sd_journal_seek_monotonic_usec()</function>, | |
142 | <function>sd_journal_seek_realtime_usec()</function>, | |
143 | and <function>sd_journal_seek_cursor()</function> | |
144 | interfaces are available as a shared library, which can | |
145 | be compiled and linked to with the | |
146 | <constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> | |
147 | file.</para> | |
148 | </refsect1> | |
149 | ||
150 | <refsect1> | |
151 | <title>See Also</title> | |
152 | ||
153 | <para> | |
154 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
155 | <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
156 | <citerefentry><refentrytitle>sd_journal_open</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
157 | <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
158 | <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
159 | <citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
160 | <citerefentry><refentrytitle>sd_journal_get_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
161 | </para> | |
162 | </refsect1> | |
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163 | |
164 | </refentry> |