summaryrefslogtreecommitdiffstats
path: root/man/sd_journal_open.xml
blob: 76b857b9916e7a0faf194d4a47f067a02701d2b8 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
<?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">

<!--
  This file is part of systemd.

  Copyright 2012 Lennart Poettering

  systemd is free software; you can redistribute it and/or modify it
  under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation; either version 2.1 of the License, or
  (at your option) any later version.

  systemd is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->

<refentry id="sd_journal_open">

        <refentryinfo>
                <title>sd_journal_open</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_open</refentrytitle>
                <manvolnum>3</manvolnum>
        </refmeta>

        <refnamediv>
                <refname>sd_journal_open</refname>
                <refname>sd_journal_open_directory</refname>
                <refname>sd_journal_close</refname>
                <refname>sd_journal</refname>
                <refname>SD_JOURNAL_LOCAL_ONLY</refname>
                <refname>SD_JOURNAL_RUNTIME_ONLY</refname>
                <refname>SD_JOURNAL_SYSTEM_ONLY</refname>
                <refpurpose>Open the system journal for reading</refpurpose>
        </refnamediv>

        <refsynopsisdiv>
                <funcsynopsis>
                        <funcsynopsisinfo>#include &lt;systemd/sd-journal.h&gt;</funcsynopsisinfo>

                        <funcprototype>
                                <funcdef>int <function>sd_journal_open</function></funcdef>
                                <paramdef>sd_journal** <parameter>ret</parameter></paramdef>
                                <paramdef>int <parameter>flags</parameter></paramdef>
                        </funcprototype>

                        <funcprototype>
                                <funcdef>int <function>sd_journal_open_directory</function></funcdef>
                                <paramdef>sd_journal** <parameter>ret</parameter></paramdef>
                                <paramdef>const char* <parameter>path</parameter></paramdef>
                                <paramdef>int <parameter>flags</parameter></paramdef>
                        </funcprototype>

                        <funcprototype>
                                <funcdef>void <function>sd_journal_close</function></funcdef>
                                <paramdef>sd_journal* <parameter>j</parameter></paramdef>
                        </funcprototype>
                </funcsynopsis>
        </refsynopsisdiv>

        <refsect1>
                <title>Description</title>

                <para><function>sd_journal_open()</function> opens
                the log journal for reading. It will find all journal
                files automatically and interleave them automatically
                when reading. As first argument it takes a pointer to
                a <literal>sd_journal</literal> pointer, which on
                success will contain journal context object afterwards. The
                second argument is a flags field, which may consist of
                the following flags ORed together:
                <literal>SD_JOURNAL_LOCAL_ONLY</literal> makes sure
                only journal files generated on the local machine will
                be opened. <literal>SD_JOURNAL_RUNTIME_ONLY</literal>
                makes sure only volatile journal files will be opened,
                excluding those which are stored on persistent
                storage. <literal>SD_JOURNAL_SYSTEM_ONLY</literal>
                will ensure that only journal files of system services
                and the kernel (in opposition to user session processes) will
                be opened.</para>

                <para><function>sd_journal_open_directory()</function>
                is similar to <function>sd_journal_open()</function>
                but takes an absolute directory path as argument. All
                journal files in this directory will be opened and
                interleaved automatically. This call also takes a
                flags argument, but it must be passed as 0 as no flags
                are currently understood for this call.</para>

                <para><function>sd_journal_close()</function> will
                close the journal context allocated with
                <function>sd_journal_open()</function> or
                <function>sd_journal_open_directory()</function> and
                free its resources.</para>

                <para>When opening the journal only journal files
                accessible to the calling user will be opened. If
                journal files are not accessible to the caller this
                will be silently ignored.</para>

                <para>See
                <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
                for an example how to iterate through the journal
                after opening it with
                <function>sd_journal_open()</function>.</para>

                <para>A journal context object returned by
                <function>sd_journal_open()</function> references a
                specific journal entry as <emphasis>current</emphasis> entry,
                similar to a file seek index in a classic file system
                file, but without absolute positions. It may be
                altered with
                <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
                and
                <citerefentry><refentrytitle>sd_journal_seek_head</refentrytitle><manvolnum>3</manvolnum></citerefentry>
                and related calls. The current entry position may be
                exported in <emphasis>cursor</emphasis> strings, as accessible
                via
                <citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Cursor
                strings may be used to globally identify a specific
                journal entry in a stable way and then later to seek
                to it (or if the specific entry is not available
                locally, to its closest entry in time)
                <citerefentry><refentrytitle>sd_journal_seek_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>

                <para>Notification of journal changes is available via
                <function>sd_journal_get_fd()</function> and related
                calls.</para>
        </refsect1>

        <refsect1>
                <title>Return Value</title>

                <para>The <function>sd_journal_open()</function> and
                <function>sd_journal_open_directory()</function> calls
                return 0 on success or a negative errno-style error
                code. <function>sd_journal_close()</function> returns
                nothing.</para>
        </refsect1>

        <refsect1>
                <title>Notes</title>

                <para>The <function>sd_journal_open()</function>,
                <function>sd_journal_open_directory()</function> and
                <function>sd_journal_close()</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_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>
                </para>
        </refsect1>

</refentry>