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3bb55eee | 1 | <?xml version='1.0'?> <!--*-nxml-*--> |
3a54a157 | 2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" |
12b42c76 | 3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
0307f791 | 4 | <!-- SPDX-License-Identifier: LGPL-2.1+ --> |
3bb55eee | 5 | |
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6 | <refentry id="sd_journal_open" |
7 | xmlns:xi="http://www.w3.org/2001/XInclude"> | |
3bb55eee | 8 | |
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9 | <refentryinfo> |
10 | <title>sd_journal_open</title> | |
11 | <productname>systemd</productname> | |
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12 | </refentryinfo> |
13 | ||
14 | <refmeta> | |
15 | <refentrytitle>sd_journal_open</refentrytitle> | |
16 | <manvolnum>3</manvolnum> | |
17 | </refmeta> | |
18 | ||
19 | <refnamediv> | |
20 | <refname>sd_journal_open</refname> | |
21 | <refname>sd_journal_open_directory</refname> | |
2aab2fab | 22 | <refname>sd_journal_open_directory_fd</refname> |
798d3a52 | 23 | <refname>sd_journal_open_files</refname> |
2aab2fab | 24 | <refname>sd_journal_open_files_fd</refname> |
21dc5e82 | 25 | <refname>sd_journal_open_namespace</refname> |
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26 | <refname>sd_journal_close</refname> |
27 | <refname>sd_journal</refname> | |
28 | <refname>SD_JOURNAL_LOCAL_ONLY</refname> | |
29 | <refname>SD_JOURNAL_RUNTIME_ONLY</refname> | |
30 | <refname>SD_JOURNAL_SYSTEM</refname> | |
31 | <refname>SD_JOURNAL_CURRENT_USER</refname> | |
2aab2fab | 32 | <refname>SD_JOURNAL_OS_ROOT</refname> |
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33 | <refname>SD_JOURNAL_ALL_NAMESPACES</refname> |
34 | <refname>SD_JOURNAL_INCLUDE_DEFAULT_NAMESPACE</refname> | |
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35 | <refpurpose>Open the system journal for reading</refpurpose> |
36 | </refnamediv> | |
37 | ||
38 | <refsynopsisdiv> | |
39 | <funcsynopsis> | |
40 | <funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo> | |
41 | ||
42 | <funcprototype> | |
43 | <funcdef>int <function>sd_journal_open</function></funcdef> | |
44 | <paramdef>sd_journal **<parameter>ret</parameter></paramdef> | |
45 | <paramdef>int <parameter>flags</parameter></paramdef> | |
46 | </funcprototype> | |
47 | ||
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48 | <funcprototype> |
49 | <funcdef>int <function>sd_journal_open_namespace</function></funcdef> | |
50 | <paramdef>sd_journal **<parameter>ret</parameter></paramdef> | |
51 | <paramdef>const char *<parameter>namespace</parameter></paramdef> | |
52 | <paramdef>int <parameter>flags</parameter></paramdef> | |
53 | </funcprototype> | |
54 | ||
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55 | <funcprototype> |
56 | <funcdef>int <function>sd_journal_open_directory</function></funcdef> | |
57 | <paramdef>sd_journal **<parameter>ret</parameter></paramdef> | |
58 | <paramdef>const char *<parameter>path</parameter></paramdef> | |
59 | <paramdef>int <parameter>flags</parameter></paramdef> | |
60 | </funcprototype> | |
61 | ||
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62 | <funcprototype> |
63 | <funcdef>int <function>sd_journal_open_directory_fd</function></funcdef> | |
64 | <paramdef>sd_journal **<parameter>ret</parameter></paramdef> | |
65 | <paramdef>int <parameter>fd</parameter></paramdef> | |
66 | <paramdef>int <parameter>flags</parameter></paramdef> | |
67 | </funcprototype> | |
68 | ||
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69 | <funcprototype> |
70 | <funcdef>int <function>sd_journal_open_files</function></funcdef> | |
71 | <paramdef>sd_journal **<parameter>ret</parameter></paramdef> | |
72 | <paramdef>const char **<parameter>paths</parameter></paramdef> | |
73 | <paramdef>int <parameter>flags</parameter></paramdef> | |
74 | </funcprototype> | |
75 | ||
76 | <funcprototype> | |
2aab2fab | 77 | <funcdef>int <function>sd_journal_open_files_fd</function></funcdef> |
798d3a52 | 78 | <paramdef>sd_journal **<parameter>ret</parameter></paramdef> |
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79 | <paramdef>int <parameter>fds[]</parameter></paramdef> |
80 | <paramdef>unsigned <parameter>n_fds</parameter></paramdef> | |
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81 | <paramdef>int <parameter>flags</parameter></paramdef> |
82 | </funcprototype> | |
83 | ||
84 | <funcprototype> | |
85 | <funcdef>void <function>sd_journal_close</function></funcdef> | |
86 | <paramdef>sd_journal *<parameter>j</parameter></paramdef> | |
87 | </funcprototype> | |
88 | </funcsynopsis> | |
89 | </refsynopsisdiv> | |
90 | ||
91 | <refsect1> | |
92 | <title>Description</title> | |
93 | ||
94 | <para><function>sd_journal_open()</function> opens the log journal | |
95 | for reading. It will find all journal files automatically and | |
96 | interleave them automatically when reading. As first argument it | |
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97 | takes a pointer to a <varname>sd_journal</varname> pointer, which, |
98 | on success, will contain a journal context object. The second | |
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99 | argument is a flags field, which may consist of the following |
100 | flags ORed together: <constant>SD_JOURNAL_LOCAL_ONLY</constant> | |
101 | makes sure only journal files generated on the local machine will | |
102 | be opened. <constant>SD_JOURNAL_RUNTIME_ONLY</constant> makes sure | |
103 | only volatile journal files will be opened, excluding those which | |
104 | are stored on persistent storage. | |
105 | <constant>SD_JOURNAL_SYSTEM</constant> will cause journal files of | |
106 | system services and the kernel (in opposition to user session | |
107 | processes) to be opened. | |
108 | <constant>SD_JOURNAL_CURRENT_USER</constant> will cause journal | |
109 | files of the current user to be opened. If neither | |
110 | <constant>SD_JOURNAL_SYSTEM</constant> nor | |
111 | <constant>SD_JOURNAL_CURRENT_USER</constant> are specified, all | |
112 | journal file types will be opened.</para> | |
113 | ||
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114 | <para><function>sd_journal_open_namespace()</function> is similar to |
115 | <function>sd_journal_open()</function> but takes an additional <parameter>namespace</parameter> parameter | |
116 | that specifies which journal namespace to operate on. If specified as <constant>NULL</constant> the call | |
117 | is identical to <function>sd_journal_open()</function>. If non-<constant>NULL</constant> only data from | |
118 | the namespace identified by the specified parameter is accessed. This call understands two additional | |
119 | flags: if <constant>SD_JOURNAL_ALL_NAMESPACES</constant> is specified the | |
120 | <parameter>namespace</parameter> parameter is ignored and all defined namespaces are accessed | |
121 | simultaneously; if <constant>SD_JOURNAL_INCLUDE_DEFAULT_NAMESPACE</constant> the specified namespace and | |
122 | the default namespace are accessed but no others (this flag has no effect when | |
123 | <parameter>namespace</parameter> is passed as <constant>NULL</constant>). For details about journal | |
124 | namespaces see | |
125 | <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para> | |
126 | ||
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127 | <para><function>sd_journal_open_directory()</function> is similar to <function>sd_journal_open()</function> but |
128 | takes an absolute directory path as argument. All journal files in this directory will be opened and interleaved | |
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129 | automatically. This call also takes a flags argument. The flags parameters accepted by this call are |
130 | <constant>SD_JOURNAL_OS_ROOT</constant>, <constant>SD_JOURNAL_SYSTEM</constant>, and | |
131 | <constant>SD_JOURNAL_CURRENT_USER</constant>. If <constant>SD_JOURNAL_OS_ROOT</constant> is specified, journal | |
132 | files are searched for below the usual <filename>/var/log/journal</filename> and | |
133 | <filename>/run/log/journal</filename> relative to the specified path, instead of directly beneath it. | |
134 | The other two flags limit which files are opened, the same as for <function>sd_journal_open()</function>. | |
135 | </para> | |
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136 | |
137 | <para><function>sd_journal_open_directory_fd()</function> is similar to | |
138 | <function>sd_journal_open_directory()</function>, but takes a file descriptor referencing a directory in the file | |
139 | system instead of an absolute file system path.</para> | |
140 | ||
141 | <para><function>sd_journal_open_files()</function> is similar to <function>sd_journal_open()</function> but takes a | |
142 | <constant>NULL</constant>-terminated list of file paths to open. All files will be opened and interleaved | |
143 | automatically. This call also takes a flags argument, but it must be passed as 0 as no flags are currently | |
144 | understood for this call. Please note that in the case of a live journal, this function is only useful for | |
145 | debugging, because individual journal files can be rotated at any moment, and the opening of specific files is | |
146 | inherently racy.</para> | |
147 | ||
148 | <para><function>sd_journal_open_files_fd()</function> is similar to <function>sd_journal_open_files()</function> | |
149 | but takes an array of open file descriptors that must reference journal files, instead of an array of file system | |
150 | paths. Pass the array of file descriptors as second argument, and the number of array entries in the third. The | |
151 | flags parameter must be passed as 0.</para> | |
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152 | |
153 | <para><varname>sd_journal</varname> objects cannot be used in the | |
154 | child after a fork. Functions which take a journal object as an | |
155 | argument (<function>sd_journal_next()</function> and others) will | |
156 | return <constant>-ECHILD</constant> after a fork. | |
157 | </para> | |
158 | ||
159 | <para><function>sd_journal_close()</function> will close the | |
160 | journal context allocated with | |
161 | <function>sd_journal_open()</function> or | |
162 | <function>sd_journal_open_directory()</function> and free its | |
163 | resources.</para> | |
164 | ||
165 | <para>When opening the journal only journal files accessible to | |
166 | the calling user will be opened. If journal files are not | |
167 | accessible to the caller, this will be silently ignored.</para> | |
168 | ||
169 | <para>See | |
170 | <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
171 | for an example of how to iterate through the journal after opening | |
172 | it with <function>sd_journal_open()</function>.</para> | |
173 | ||
174 | <para>A journal context object returned by | |
175 | <function>sd_journal_open()</function> references a specific | |
176 | journal entry as <emphasis>current</emphasis> entry, similar to a | |
177 | file seek index in a classic file system file, but without | |
178 | absolute positions. It may be altered with | |
179 | <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
180 | and | |
181 | <citerefentry><refentrytitle>sd_journal_seek_head</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
182 | and related calls. The current entry position may be exported in | |
183 | <emphasis>cursor</emphasis> strings, as accessible via | |
184 | <citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>. | |
185 | Cursor strings may be used to globally identify a specific journal | |
186 | entry in a stable way and then later to seek to it (or if the | |
187 | specific entry is not available locally, to its closest entry in | |
188 | time) | |
189 | <citerefentry><refentrytitle>sd_journal_seek_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> | |
190 | ||
191 | <para>Notification of journal changes is available via | |
192 | <function>sd_journal_get_fd()</function> and related calls.</para> | |
193 | </refsect1> | |
194 | ||
195 | <refsect1> | |
196 | <title>Return Value</title> | |
197 | ||
198 | <para>The <function>sd_journal_open()</function>, | |
199 | <function>sd_journal_open_directory()</function>, and | |
200 | <function>sd_journal_open_files()</function> calls return 0 on | |
201 | success or a negative errno-style error code. | |
202 | <function>sd_journal_close()</function> returns nothing.</para> | |
203 | </refsect1> | |
204 | ||
205 | <refsect1> | |
206 | <title>Notes</title> | |
207 | ||
64a7ef8b | 208 | <xi:include href="threads-aware.xml" xpointer="strict"/> |
a8d46a16 | 209 | |
64a7ef8b | 210 | <xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/> |
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211 | </refsect1> |
212 | ||
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213 | <refsect1> |
214 | <title>See Also</title> | |
215 | ||
216 | <para> | |
217 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
218 | <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
d18df32d | 219 | <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, |
798d3a52 | 220 | <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
d18df32d | 221 | <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
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222 | </para> |
223 | </refsect1> | |
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224 | |
225 | </refentry> |