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