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2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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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.
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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_open_files</refname>
49 <refname>sd_journal_open_container</refname>
50 <refname>sd_journal_close</refname>
51 <refname>sd_journal</refname>
52 <refname>SD_JOURNAL_LOCAL_ONLY</refname>
53 <refname>SD_JOURNAL_RUNTIME_ONLY</refname>
54 <refname>SD_JOURNAL_SYSTEM</refname>
55 <refname>SD_JOURNAL_CURRENT_USER</refname>
56 <refpurpose>Open the system journal for reading</refpurpose>
61 <funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo>
64 <funcdef>int <function>sd_journal_open</function></funcdef>
65 <paramdef>sd_journal **<parameter>ret</parameter></paramdef>
66 <paramdef>int <parameter>flags</parameter></paramdef>
70 <funcdef>int <function>sd_journal_open_directory</function></funcdef>
71 <paramdef>sd_journal **<parameter>ret</parameter></paramdef>
72 <paramdef>const char *<parameter>path</parameter></paramdef>
73 <paramdef>int <parameter>flags</parameter></paramdef>
77 <funcdef>int <function>sd_journal_open_files</function></funcdef>
78 <paramdef>sd_journal **<parameter>ret</parameter></paramdef>
79 <paramdef>const char **<parameter>paths</parameter></paramdef>
80 <paramdef>int <parameter>flags</parameter></paramdef>
84 <funcdef>int <function>sd_journal_open_container</function></funcdef>
85 <paramdef>sd_journal **<parameter>ret</parameter></paramdef>
86 <paramdef>const char *<parameter>machine</parameter></paramdef>
87 <paramdef>int <parameter>flags</parameter></paramdef>
91 <funcdef>void <function>sd_journal_close</function></funcdef>
92 <paramdef>sd_journal *<parameter>j</parameter></paramdef>
98 <title>Description</title>
100 <para><function>sd_journal_open()</function> opens
101 the log journal for reading. It will find all journal
102 files automatically and interleave them automatically
103 when reading. As first argument it takes a pointer to
104 a <varname>sd_journal</varname> pointer, which on
105 success will contain a journal context object. The
106 second argument is a flags field, which may consist of
107 the following flags ORed together:
108 <constant>SD_JOURNAL_LOCAL_ONLY</constant> makes sure
109 only journal files generated on the local machine will
110 be opened. <constant>SD_JOURNAL_RUNTIME_ONLY</constant>
111 makes sure only volatile journal files will be opened,
112 excluding those which are stored on persistent
113 storage. <constant>SD_JOURNAL_SYSTEM</constant>
114 will cause journal files of system services and the
115 kernel (in opposition to user session processes) to
116 be opened. <constant>SD_JOURNAL_CURRENT_USER</constant>
117 will cause journal files of the current user to be
118 opened. If neither <constant>SD_JOURNAL_SYSTEM</constant>
119 nor <constant>SD_JOURNAL_CURRENT_USER</constant> are
120 specified, all journal file types will be opened.</para>
122 <para><function>sd_journal_open_directory()</function>
123 is similar to <function>sd_journal_open()</function>
124 but takes an absolute directory path as argument. All
125 journal files in this directory will be opened and
126 interleaved automatically. This call also takes a
127 flags argument, but it must be passed as 0 as no flags
128 are currently understood for this call.</para>
130 <para><function>sd_journal_open_files()</function>
131 is similar to <function>sd_journal_open()</function>
132 but takes a <constant>NULL</constant>-terminated list
133 of file paths to open. All files will be opened and
134 interleaved automatically. This call also takes a
135 flags argument, but it must be passed as 0 as no flags
136 are currently understood for this call. Please note
137 that in the case of a live journal, this function is only
138 useful for debugging, because individual journal files
139 can be rotated at any moment, and the opening of
140 specific files is inherently racy.</para>
142 <para><function>sd_journal_open_container()</function>
143 is similar to <function>sd_journal_open()</function>
144 but opens the journal files of a running
145 OS container. The specified machine name refers to a
146 container that is registered with
147 <citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
149 <para><varname>sd_journal</varname> objects cannot be
150 used in the child after a fork. Functions which take a
151 journal object as an argument
152 (<function>sd_journal_next()</function> and others)
153 will return <constant>-ECHILD</constant> after a fork.
156 <para><function>sd_journal_close()</function> will
157 close the journal context allocated with
158 <function>sd_journal_open()</function> or
159 <function>sd_journal_open_directory()</function> and
160 free its resources.</para>
162 <para>When opening the journal only journal files
163 accessible to the calling user will be opened. If
164 journal files are not accessible to the caller, this
165 will be silently ignored.</para>
168 <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
169 for an example of how to iterate through the journal
170 after opening it with
171 <function>sd_journal_open()</function>.</para>
173 <para>A journal context object returned by
174 <function>sd_journal_open()</function> references a
175 specific journal entry as <emphasis>current</emphasis> entry,
176 similar to a file seek index in a classic file system
177 file, but without absolute positions. It may be
179 <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
181 <citerefentry><refentrytitle>sd_journal_seek_head</refentrytitle><manvolnum>3</manvolnum></citerefentry>
182 and related calls. The current entry position may be
183 exported in <emphasis>cursor</emphasis> strings, as accessible
185 <citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Cursor
186 strings may be used to globally identify a specific
187 journal entry in a stable way and then later to seek
188 to it (or if the specific entry is not available
189 locally, to its closest entry in time)
190 <citerefentry><refentrytitle>sd_journal_seek_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
192 <para>Notification of journal changes is available via
193 <function>sd_journal_get_fd()</function> and related
198 <title>Return Value</title>
200 <para>The <function>sd_journal_open()</function>,
201 <function>sd_journal_open_directory()</function>, and
202 <function>sd_journal_open_files()</function> calls
203 return 0 on success or a negative errno-style error
204 code. <function>sd_journal_close()</function> returns
211 <para>The <function>sd_journal_open()</function>,
212 <function>sd_journal_open_directory()</function> and
213 <function>sd_journal_close()</function> interfaces are
214 available as a shared library, which can be compiled and
216 <constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
221 <title>History</title>
223 <para><function>sd_journal_open()</function>,
224 <function>sd_journal_close()</function>,
225 <constant>SD_JOURNAL_LOCAL_ONLY</constant>,
226 <constant>SD_JOURNAL_RUNTIME_ONLY</constant>,
227 <constant>SD_JOURNAL_SYSTEM_ONLY</constant> were added
228 in systemd-38.</para>
230 <para><function>sd_journal_open_directory()</function>
231 was added in systemd-187.</para>
233 <para><constant>SD_JOURNAL_SYSTEM</constant>,
234 <constant>SD_JOURNAL_CURRENT_USER</constant>,
235 and <function>sd_journal_open_files()</function>
236 were added in systemd-205.
237 <constant>SD_JOURNAL_SYSTEM_ONLY</constant>
238 was deprecated.</para>
242 <title>See Also</title>
245 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
246 <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
247 <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
248 <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
249 <citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry>