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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 | <!-- | |
6 | This file is part of systemd. | |
7 | ||
8 | Copyright 2012 Lennart Poettering | |
9 | ||
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. | |
14 | ||
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. | |
19 | ||
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/>. | |
22 | --> | |
23 | ||
24 | <refentry id="sd_journal_open"> | |
25 | ||
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26 | <refentryinfo> |
27 | <title>sd_journal_open</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_open</refentrytitle> | |
42 | <manvolnum>3</manvolnum> | |
43 | </refmeta> | |
44 | ||
45 | <refnamediv> | |
46 | <refname>sd_journal_open</refname> | |
47 | <refname>sd_journal_open_directory</refname> | |
2aab2fab | 48 | <refname>sd_journal_open_directory_fd</refname> |
798d3a52 | 49 | <refname>sd_journal_open_files</refname> |
2aab2fab | 50 | <refname>sd_journal_open_files_fd</refname> |
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51 | <refname>sd_journal_close</refname> |
52 | <refname>sd_journal</refname> | |
53 | <refname>SD_JOURNAL_LOCAL_ONLY</refname> | |
54 | <refname>SD_JOURNAL_RUNTIME_ONLY</refname> | |
55 | <refname>SD_JOURNAL_SYSTEM</refname> | |
56 | <refname>SD_JOURNAL_CURRENT_USER</refname> | |
2aab2fab | 57 | <refname>SD_JOURNAL_OS_ROOT</refname> |
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58 | <refpurpose>Open the system journal for reading</refpurpose> |
59 | </refnamediv> | |
60 | ||
61 | <refsynopsisdiv> | |
62 | <funcsynopsis> | |
63 | <funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo> | |
64 | ||
65 | <funcprototype> | |
66 | <funcdef>int <function>sd_journal_open</function></funcdef> | |
67 | <paramdef>sd_journal **<parameter>ret</parameter></paramdef> | |
68 | <paramdef>int <parameter>flags</parameter></paramdef> | |
69 | </funcprototype> | |
70 | ||
71 | <funcprototype> | |
72 | <funcdef>int <function>sd_journal_open_directory</function></funcdef> | |
73 | <paramdef>sd_journal **<parameter>ret</parameter></paramdef> | |
74 | <paramdef>const char *<parameter>path</parameter></paramdef> | |
75 | <paramdef>int <parameter>flags</parameter></paramdef> | |
76 | </funcprototype> | |
77 | ||
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78 | <funcprototype> |
79 | <funcdef>int <function>sd_journal_open_directory_fd</function></funcdef> | |
80 | <paramdef>sd_journal **<parameter>ret</parameter></paramdef> | |
81 | <paramdef>int <parameter>fd</parameter></paramdef> | |
82 | <paramdef>int <parameter>flags</parameter></paramdef> | |
83 | </funcprototype> | |
84 | ||
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85 | <funcprototype> |
86 | <funcdef>int <function>sd_journal_open_files</function></funcdef> | |
87 | <paramdef>sd_journal **<parameter>ret</parameter></paramdef> | |
88 | <paramdef>const char **<parameter>paths</parameter></paramdef> | |
89 | <paramdef>int <parameter>flags</parameter></paramdef> | |
90 | </funcprototype> | |
91 | ||
92 | <funcprototype> | |
2aab2fab | 93 | <funcdef>int <function>sd_journal_open_files_fd</function></funcdef> |
798d3a52 | 94 | <paramdef>sd_journal **<parameter>ret</parameter></paramdef> |
2aab2fab LP |
95 | <paramdef>int <parameter>fds[]</parameter></paramdef> |
96 | <paramdef>unsigned <parameter>n_fds</parameter></paramdef> | |
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97 | <paramdef>int <parameter>flags</parameter></paramdef> |
98 | </funcprototype> | |
99 | ||
100 | <funcprototype> | |
101 | <funcdef>void <function>sd_journal_close</function></funcdef> | |
102 | <paramdef>sd_journal *<parameter>j</parameter></paramdef> | |
103 | </funcprototype> | |
104 | </funcsynopsis> | |
105 | </refsynopsisdiv> | |
106 | ||
107 | <refsect1> | |
108 | <title>Description</title> | |
109 | ||
110 | <para><function>sd_journal_open()</function> opens the log journal | |
111 | for reading. It will find all journal files automatically and | |
112 | interleave them automatically when reading. As first argument it | |
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113 | takes a pointer to a <varname>sd_journal</varname> pointer, which, |
114 | on success, will contain a journal context object. The second | |
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115 | argument is a flags field, which may consist of the following |
116 | flags ORed together: <constant>SD_JOURNAL_LOCAL_ONLY</constant> | |
117 | makes sure only journal files generated on the local machine will | |
118 | be opened. <constant>SD_JOURNAL_RUNTIME_ONLY</constant> makes sure | |
119 | only volatile journal files will be opened, excluding those which | |
120 | are stored on persistent storage. | |
121 | <constant>SD_JOURNAL_SYSTEM</constant> will cause journal files of | |
122 | system services and the kernel (in opposition to user session | |
123 | processes) to be opened. | |
124 | <constant>SD_JOURNAL_CURRENT_USER</constant> will cause journal | |
125 | files of the current user to be opened. If neither | |
126 | <constant>SD_JOURNAL_SYSTEM</constant> nor | |
127 | <constant>SD_JOURNAL_CURRENT_USER</constant> are specified, all | |
128 | journal file types will be opened.</para> | |
129 | ||
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130 | <para><function>sd_journal_open_directory()</function> is similar to <function>sd_journal_open()</function> but |
131 | takes an absolute directory path as argument. All journal files in this directory will be opened and interleaved | |
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132 | automatically. This call also takes a flags argument. The flags parameters accepted by this call are |
133 | <constant>SD_JOURNAL_OS_ROOT</constant>, <constant>SD_JOURNAL_SYSTEM</constant>, and | |
134 | <constant>SD_JOURNAL_CURRENT_USER</constant>. If <constant>SD_JOURNAL_OS_ROOT</constant> is specified, journal | |
135 | files are searched for below the usual <filename>/var/log/journal</filename> and | |
136 | <filename>/run/log/journal</filename> relative to the specified path, instead of directly beneath it. | |
137 | The other two flags limit which files are opened, the same as for <function>sd_journal_open()</function>. | |
138 | </para> | |
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139 | |
140 | <para><function>sd_journal_open_directory_fd()</function> is similar to | |
141 | <function>sd_journal_open_directory()</function>, but takes a file descriptor referencing a directory in the file | |
142 | system instead of an absolute file system path.</para> | |
143 | ||
144 | <para><function>sd_journal_open_files()</function> is similar to <function>sd_journal_open()</function> but takes a | |
145 | <constant>NULL</constant>-terminated list of file paths to open. All files will be opened and interleaved | |
146 | automatically. This call also takes a flags argument, but it must be passed as 0 as no flags are currently | |
147 | understood for this call. Please note that in the case of a live journal, this function is only useful for | |
148 | debugging, because individual journal files can be rotated at any moment, and the opening of specific files is | |
149 | inherently racy.</para> | |
150 | ||
151 | <para><function>sd_journal_open_files_fd()</function> is similar to <function>sd_journal_open_files()</function> | |
152 | but takes an array of open file descriptors that must reference journal files, instead of an array of file system | |
153 | paths. Pass the array of file descriptors as second argument, and the number of array entries in the third. The | |
154 | flags parameter must be passed as 0.</para> | |
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155 | |
156 | <para><varname>sd_journal</varname> objects cannot be used in the | |
157 | child after a fork. Functions which take a journal object as an | |
158 | argument (<function>sd_journal_next()</function> and others) will | |
159 | return <constant>-ECHILD</constant> after a fork. | |
160 | </para> | |
161 | ||
162 | <para><function>sd_journal_close()</function> will close the | |
163 | journal context allocated with | |
164 | <function>sd_journal_open()</function> or | |
165 | <function>sd_journal_open_directory()</function> and free its | |
166 | resources.</para> | |
167 | ||
168 | <para>When opening the journal only journal files accessible to | |
169 | the calling user will be opened. If journal files are not | |
170 | accessible to the caller, this will be silently ignored.</para> | |
171 | ||
172 | <para>See | |
173 | <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
174 | for an example of how to iterate through the journal after opening | |
175 | it with <function>sd_journal_open()</function>.</para> | |
176 | ||
177 | <para>A journal context object returned by | |
178 | <function>sd_journal_open()</function> references a specific | |
179 | journal entry as <emphasis>current</emphasis> entry, similar to a | |
180 | file seek index in a classic file system file, but without | |
181 | absolute positions. It may be altered with | |
182 | <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
183 | and | |
184 | <citerefentry><refentrytitle>sd_journal_seek_head</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
185 | and related calls. The current entry position may be exported in | |
186 | <emphasis>cursor</emphasis> strings, as accessible via | |
187 | <citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>. | |
188 | Cursor strings may be used to globally identify a specific journal | |
189 | entry in a stable way and then later to seek to it (or if the | |
190 | specific entry is not available locally, to its closest entry in | |
191 | time) | |
192 | <citerefentry><refentrytitle>sd_journal_seek_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> | |
193 | ||
194 | <para>Notification of journal changes is available via | |
195 | <function>sd_journal_get_fd()</function> and related calls.</para> | |
196 | </refsect1> | |
197 | ||
198 | <refsect1> | |
199 | <title>Return Value</title> | |
200 | ||
201 | <para>The <function>sd_journal_open()</function>, | |
202 | <function>sd_journal_open_directory()</function>, and | |
203 | <function>sd_journal_open_files()</function> calls return 0 on | |
204 | success or a negative errno-style error code. | |
205 | <function>sd_journal_close()</function> returns nothing.</para> | |
206 | </refsect1> | |
207 | ||
208 | <refsect1> | |
209 | <title>Notes</title> | |
210 | ||
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211 | <para>All functions listed here are thread-agnostic and only a single thread may operate |
212 | on a given <structname>sd_journal</structname> object.</para> | |
213 | ||
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214 | <para>The <function>sd_journal_open()</function>, |
215 | <function>sd_journal_open_directory()</function> and | |
216 | <function>sd_journal_close()</function> interfaces are available | |
217 | as a shared library, which can be compiled and linked to with the | |
218 | <constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> | |
219 | file.</para> | |
220 | </refsect1> | |
221 | ||
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222 | <refsect1> |
223 | <title>See Also</title> | |
224 | ||
225 | <para> | |
226 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
227 | <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
228 | <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
229 | <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
230 | <citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
231 | </para> | |
232 | </refsect1> | |
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233 | |
234 | </refentry> |