chiark / gitweb /
net-util: add support for Type=ethernet
[elogind.git] / man / sd_journal_seek_head.xml
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
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8   Copyright 2012 Lennart Poettering
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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 &lt;systemd/sd-journal.h&gt;</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
95                 available entry.</para>
96
97                 <para>Similarly,
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
104                 timestamp,
105                 i.e. <constant>CLOCK_MONOTONIC</constant>. Since
106                 monotonic time restarts on every reboot a boot ID
107                 needs to be specified as well.</para>
108
109                 <para><function>sd_journal_seek_realtime_usec()</function>
110                 seeks to the entry with the specified realtime
111                 (wallclock) timestamp,
112                 i.e. <constant>CLOCK_REALTIME</constant>. Note that
113                 the realtime clock is not necessarily monotonic. If a
114                 realtime timestamp is ambiguous, it is not defined
115                 which position is sought to.</para>
116
117                 <para><function>sd_journal_seek_cursor()</function>
118                 seeks to the entry located at the specified cursor
119                 string. For details on cursors, see
120                 <citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If
121                 no entry matching the specified cursor is found the
122                 call will seek to the next closest entry (in terms of
123                 time) instead. To verify whether the newly selected
124                 entry actually matches the cursor, use
125                 <citerefentry><refentrytitle>sd_journal_test_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
126
127                 <para>Note that these calls do not actually make any
128                 entry the new current entry, this needs to be done in
129                 a separate step with a subsequent
130                 <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
131                 invocation (or a similar call). Only then, entry data
132                 may be retrieved via
133                 <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If
134                 no entry exists that matches exactly the specified
135                 seek address, the next closest is sought to. If
136                 <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
137                 is used, the closest following entry will be sought to,
138                 if
139                 <citerefentry><refentrytitle>sd_journal_previous</refentrytitle><manvolnum>3</manvolnum></citerefentry>
140                 is used the closest preceding entry is sought
141                 to.</para>
142         </refsect1>
143
144         <refsect1>
145                 <title>Return Value</title>
146
147                 <para>The functions return 0 on success or a negative
148                 errno-style error code.</para>
149         </refsect1>
150
151         <refsect1>
152                 <title>Notes</title>
153
154                 <para>The <function>sd_journal_seek_head()</function>,
155                 <function>sd_journal_seek_tail()</function>,
156                 <function>sd_journal_seek_monotonic_usec()</function>,
157                 <function>sd_journal_seek_realtime_usec()</function>,
158                 and <function>sd_journal_seek_cursor()</function>
159                 interfaces are available as a shared library, which can
160                 be compiled and linked to with the
161                 <constant>libsystemd-journal</constant> <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
162                 file.</para>
163         </refsect1>
164
165         <refsect1>
166                 <title>See Also</title>
167
168                 <para>
169                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
170                         <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
171                         <citerefentry><refentrytitle>sd_journal_open</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
172                         <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
173                         <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
174                         <citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
175                         <citerefentry><refentrytitle>sd_journal_get_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>
176                 </para>
177         </refsect1>
178
179 </refentry>