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">
6 This file is part of systemd.
8 Copyright 2012 Lennart Poettering
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.
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.
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/>.
24 <refentry id="sd_journal_open">
27 <title>sd_journal_open</title>
28 <productname>systemd</productname>
32 <contrib>Developer</contrib>
33 <firstname>Lennart</firstname>
34 <surname>Poettering</surname>
35 <email>lennart@poettering.net</email>
41 <refentrytitle>sd_journal_open</refentrytitle>
42 <manvolnum>3</manvolnum>
46 <refname>sd_journal_open</refname>
47 <refname>sd_journal_open_directory</refname>
48 <refname>sd_journal_close</refname>
49 <refpurpose>Open the system journal for reading</refpurpose>
54 <funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo>
57 <funcdef>int <function>sd_journal_open</function></funcdef>
58 <paramdef>sd_journal** <parameter>ret</parameter></paramdef>
59 <paramdef>int <parameter>flags</parameter></paramdef>
63 <funcdef>int <function>sd_journal_open_directory</function></funcdef>
64 <paramdef>sd_journal** <parameter>ret</parameter></paramdef>
65 <paramdef>const char* <parameter>path</parameter></paramdef>
66 <paramdef>int <parameter>flags</parameter></paramdef>
70 <funcdef>int <function>sd_journal_close</function></funcdef>
71 <paramdef>sd_journal* <parameter>j</parameter></paramdef>
77 <title>Description</title>
79 <para><function>sd_journal_open()</function> opens the
80 the log journal for reading. It will find all journal
81 files automatically and interleave them automatically
82 when reading. As first argument it takes a pointer to
83 a <literal>sd_journal</literal> pointer, which on
84 success will contain journal context afterwards. The
85 second argument is a flags field, which may consist of
86 the following flags ORed together:
87 <literal>SD_JOURNAL_LOCAL_ONLY</literal> makes sure
88 only journal files generated on the local machine will
89 be opened. <literal>SD_JOURNAL_RUNTIME_ONLY</literal>
90 makes sure only volatile journal files will be opened,
91 excluding those which are stored on persistant
92 storage. <literal>SD_JOURNAL_SYSTEM_ONLY</literal>
93 will ensure that only journal files of system services
94 and the kernel (in opposition to user session processes) will
97 <para><function>sd_journal_open_directory()</function>
98 is similar to <function>sd_journal_open()</function>
99 but takes an absolute directory path as argument. All
100 journal files in this directory will be opened and
101 interleaved automatically. This call also takes a
102 flags argument, but it must be passed as 0 as no flags
103 are currently understood for this call.</para>
105 <para><function>sd_journal_close()</function> will
106 close the journal context allocated with
107 <function>sd_journal_open()</function> or
108 <function>sd_journal_open_directory()</function> and
109 free its resources.</para>
111 <para>When opening the journal only journal files
112 accessible to the calling user will be opened. If
113 journal files are not accessible to the caller this
114 will be silently ignored.</para>
117 <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
118 for an example how to iterate through the journal
119 after opening it it with
120 <function>sd_journal_open()</function>.</para>
122 <para>A journal context object returned by
123 <function>sd_journal_open()</function> references a
124 specific journal entry as <emphasis>current</emphasis> entry,
125 similar to a file seek index in a classic file system
126 file, but without absolute positions. It may be
128 <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
130 <citerefentry><refentrytitle>sd_journal_seek_head</refentrytitle><manvolnum>3</manvolnum></citerefentry>
131 and related calls. The current entry position may be
132 exported in <emphasis>cursor</emphasis> strings, as accessible
134 <citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Cursor
135 strings may be used to globally identify a specific
136 journal entry in a stable way and then later to seek
137 to it (or if the specific entry is not available
138 locally, to its closest entry in time)
139 <citerefentry><refentrytitle>sd_journal_seek_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
141 <para>Notification of journal changes is available via
142 <function>sd_journal_get_fd()</function> and related
147 <title>Return Value</title>
149 <para>The <function>sd_journal_open()</function> and
150 <function>sd_journal_open_directory()</function> calls
151 return 0 on success or a negative errno-style error
152 code. <function>sd_journal_close()</function> returns
159 <para>The <function>sd_journal_open()</function>,
160 <function>sd_journal_open_directory()</function> and
161 <function>sd_journal_close()</function> interfaces are
162 available as shared library, which can be compiled and
164 <literal>libsystemd-journal</literal>
165 <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
170 <title>See Also</title>
173 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
174 <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
175 <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
176 <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>