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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 | |
11 | ||
12 | systemd is free software; you can redistribute it and/or modify it | |
13 | under the terms of the GNU Lesser General Public License as published by | |
14 | the Free Software Foundation; either version 2.1 of the License, or | |
15 | (at your option) any later version. | |
16 | ||
17 | systemd is distributed in the hope that it will be useful, but | |
18 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
20 | Lesser General Public License for more details. | |
21 | ||
22 | You should have received a copy of the GNU Lesser General Public License | |
23 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
24 | --> | |
25 | ||
26 | <refentry id="sd_journal_open"> | |
27 | ||
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28 | <refentryinfo> |
29 | <title>sd_journal_open</title> | |
30 | <productname>systemd</productname> | |
31 | ||
32 | <authorgroup> | |
33 | <author> | |
34 | <contrib>Developer</contrib> | |
35 | <firstname>Lennart</firstname> | |
36 | <surname>Poettering</surname> | |
37 | <email>lennart@poettering.net</email> | |
38 | </author> | |
39 | </authorgroup> | |
40 | </refentryinfo> | |
41 | ||
42 | <refmeta> | |
43 | <refentrytitle>sd_journal_open</refentrytitle> | |
44 | <manvolnum>3</manvolnum> | |
45 | </refmeta> | |
46 | ||
47 | <refnamediv> | |
48 | <refname>sd_journal_open</refname> | |
49 | <refname>sd_journal_open_directory</refname> | |
2aab2fab | 50 | <refname>sd_journal_open_directory_fd</refname> |
798d3a52 | 51 | <refname>sd_journal_open_files</refname> |
2aab2fab | 52 | <refname>sd_journal_open_files_fd</refname> |
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53 | <refname>sd_journal_close</refname> |
54 | <refname>sd_journal</refname> | |
55 | <refname>SD_JOURNAL_LOCAL_ONLY</refname> | |
56 | <refname>SD_JOURNAL_RUNTIME_ONLY</refname> | |
57 | <refname>SD_JOURNAL_SYSTEM</refname> | |
58 | <refname>SD_JOURNAL_CURRENT_USER</refname> | |
2aab2fab | 59 | <refname>SD_JOURNAL_OS_ROOT</refname> |
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60 | <refpurpose>Open the system journal for reading</refpurpose> |
61 | </refnamediv> | |
62 | ||
63 | <refsynopsisdiv> | |
64 | <funcsynopsis> | |
65 | <funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo> | |
66 | ||
67 | <funcprototype> | |
68 | <funcdef>int <function>sd_journal_open</function></funcdef> | |
69 | <paramdef>sd_journal **<parameter>ret</parameter></paramdef> | |
70 | <paramdef>int <parameter>flags</parameter></paramdef> | |
71 | </funcprototype> | |
72 | ||
73 | <funcprototype> | |
74 | <funcdef>int <function>sd_journal_open_directory</function></funcdef> | |
75 | <paramdef>sd_journal **<parameter>ret</parameter></paramdef> | |
76 | <paramdef>const char *<parameter>path</parameter></paramdef> | |
77 | <paramdef>int <parameter>flags</parameter></paramdef> | |
78 | </funcprototype> | |
79 | ||
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80 | <funcprototype> |
81 | <funcdef>int <function>sd_journal_open_directory_fd</function></funcdef> | |
82 | <paramdef>sd_journal **<parameter>ret</parameter></paramdef> | |
83 | <paramdef>int <parameter>fd</parameter></paramdef> | |
84 | <paramdef>int <parameter>flags</parameter></paramdef> | |
85 | </funcprototype> | |
86 | ||
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87 | <funcprototype> |
88 | <funcdef>int <function>sd_journal_open_files</function></funcdef> | |
89 | <paramdef>sd_journal **<parameter>ret</parameter></paramdef> | |
90 | <paramdef>const char **<parameter>paths</parameter></paramdef> | |
91 | <paramdef>int <parameter>flags</parameter></paramdef> | |
92 | </funcprototype> | |
93 | ||
94 | <funcprototype> | |
2aab2fab | 95 | <funcdef>int <function>sd_journal_open_files_fd</function></funcdef> |
798d3a52 | 96 | <paramdef>sd_journal **<parameter>ret</parameter></paramdef> |
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97 | <paramdef>int <parameter>fds[]</parameter></paramdef> |
98 | <paramdef>unsigned <parameter>n_fds</parameter></paramdef> | |
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99 | <paramdef>int <parameter>flags</parameter></paramdef> |
100 | </funcprototype> | |
101 | ||
102 | <funcprototype> | |
103 | <funcdef>void <function>sd_journal_close</function></funcdef> | |
104 | <paramdef>sd_journal *<parameter>j</parameter></paramdef> | |
105 | </funcprototype> | |
106 | </funcsynopsis> | |
107 | </refsynopsisdiv> | |
108 | ||
109 | <refsect1> | |
110 | <title>Description</title> | |
111 | ||
112 | <para><function>sd_journal_open()</function> opens the log journal | |
113 | for reading. It will find all journal files automatically and | |
114 | interleave them automatically when reading. As first argument it | |
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115 | takes a pointer to a <varname>sd_journal</varname> pointer, which, |
116 | on success, will contain a journal context object. The second | |
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117 | argument is a flags field, which may consist of the following |
118 | flags ORed together: <constant>SD_JOURNAL_LOCAL_ONLY</constant> | |
119 | makes sure only journal files generated on the local machine will | |
120 | be opened. <constant>SD_JOURNAL_RUNTIME_ONLY</constant> makes sure | |
121 | only volatile journal files will be opened, excluding those which | |
122 | are stored on persistent storage. | |
123 | <constant>SD_JOURNAL_SYSTEM</constant> will cause journal files of | |
124 | system services and the kernel (in opposition to user session | |
125 | processes) to be opened. | |
126 | <constant>SD_JOURNAL_CURRENT_USER</constant> will cause journal | |
127 | files of the current user to be opened. If neither | |
128 | <constant>SD_JOURNAL_SYSTEM</constant> nor | |
129 | <constant>SD_JOURNAL_CURRENT_USER</constant> are specified, all | |
130 | journal file types will be opened.</para> | |
131 | ||
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132 | <para><function>sd_journal_open_directory()</function> is similar to <function>sd_journal_open()</function> but |
133 | takes an absolute directory path as argument. All journal files in this directory will be opened and interleaved | |
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134 | automatically. This call also takes a flags argument. The flags parameters accepted by this call are |
135 | <constant>SD_JOURNAL_OS_ROOT</constant>, <constant>SD_JOURNAL_SYSTEM</constant>, and | |
136 | <constant>SD_JOURNAL_CURRENT_USER</constant>. If <constant>SD_JOURNAL_OS_ROOT</constant> is specified, journal | |
137 | files are searched for below the usual <filename>/var/log/journal</filename> and | |
138 | <filename>/run/log/journal</filename> relative to the specified path, instead of directly beneath it. | |
139 | The other two flags limit which files are opened, the same as for <function>sd_journal_open()</function>. | |
140 | </para> | |
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141 | |
142 | <para><function>sd_journal_open_directory_fd()</function> is similar to | |
143 | <function>sd_journal_open_directory()</function>, but takes a file descriptor referencing a directory in the file | |
144 | system instead of an absolute file system path.</para> | |
145 | ||
146 | <para><function>sd_journal_open_files()</function> is similar to <function>sd_journal_open()</function> but takes a | |
147 | <constant>NULL</constant>-terminated list of file paths to open. All files will be opened and interleaved | |
148 | automatically. This call also takes a flags argument, but it must be passed as 0 as no flags are currently | |
149 | understood for this call. Please note that in the case of a live journal, this function is only useful for | |
150 | debugging, because individual journal files can be rotated at any moment, and the opening of specific files is | |
151 | inherently racy.</para> | |
152 | ||
153 | <para><function>sd_journal_open_files_fd()</function> is similar to <function>sd_journal_open_files()</function> | |
154 | but takes an array of open file descriptors that must reference journal files, instead of an array of file system | |
155 | paths. Pass the array of file descriptors as second argument, and the number of array entries in the third. The | |
156 | flags parameter must be passed as 0.</para> | |
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157 | |
158 | <para><varname>sd_journal</varname> objects cannot be used in the | |
159 | child after a fork. Functions which take a journal object as an | |
160 | argument (<function>sd_journal_next()</function> and others) will | |
161 | return <constant>-ECHILD</constant> after a fork. | |
162 | </para> | |
163 | ||
164 | <para><function>sd_journal_close()</function> will close the | |
165 | journal context allocated with | |
166 | <function>sd_journal_open()</function> or | |
167 | <function>sd_journal_open_directory()</function> and free its | |
168 | resources.</para> | |
169 | ||
170 | <para>When opening the journal only journal files accessible to | |
171 | the calling user will be opened. If journal files are not | |
172 | accessible to the caller, this will be silently ignored.</para> | |
173 | ||
174 | <para>See | |
175 | <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
176 | for an example of how to iterate through the journal after opening | |
177 | it with <function>sd_journal_open()</function>.</para> | |
178 | ||
179 | <para>A journal context object returned by | |
180 | <function>sd_journal_open()</function> references a specific | |
181 | journal entry as <emphasis>current</emphasis> entry, similar to a | |
182 | file seek index in a classic file system file, but without | |
183 | absolute positions. It may be altered with | |
184 | <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
185 | and | |
186 | <citerefentry><refentrytitle>sd_journal_seek_head</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
187 | and related calls. The current entry position may be exported in | |
188 | <emphasis>cursor</emphasis> strings, as accessible via | |
189 | <citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>. | |
190 | Cursor strings may be used to globally identify a specific journal | |
191 | entry in a stable way and then later to seek to it (or if the | |
192 | specific entry is not available locally, to its closest entry in | |
193 | time) | |
194 | <citerefentry><refentrytitle>sd_journal_seek_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> | |
195 | ||
196 | <para>Notification of journal changes is available via | |
197 | <function>sd_journal_get_fd()</function> and related calls.</para> | |
198 | </refsect1> | |
199 | ||
200 | <refsect1> | |
201 | <title>Return Value</title> | |
202 | ||
203 | <para>The <function>sd_journal_open()</function>, | |
204 | <function>sd_journal_open_directory()</function>, and | |
205 | <function>sd_journal_open_files()</function> calls return 0 on | |
206 | success or a negative errno-style error code. | |
207 | <function>sd_journal_close()</function> returns nothing.</para> | |
208 | </refsect1> | |
209 | ||
210 | <refsect1> | |
211 | <title>Notes</title> | |
212 | ||
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213 | <para>All functions listed here are thread-agnostic and only a single thread may operate |
214 | on a given <structname>sd_journal</structname> object.</para> | |
215 | ||
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216 | <para>The <function>sd_journal_open()</function>, |
217 | <function>sd_journal_open_directory()</function> and | |
218 | <function>sd_journal_close()</function> interfaces are available | |
219 | as a shared library, which can be compiled and linked to with the | |
220 | <constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> | |
221 | file.</para> | |
222 | </refsect1> | |
223 | ||
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224 | <refsect1> |
225 | <title>See Also</title> | |
226 | ||
227 | <para> | |
228 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
229 | <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
230 | <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
231 | <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
232 | <citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
233 | </para> | |
234 | </refsect1> | |
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235 | |
236 | </refentry> |