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1 | <?xml version='1.0'?> <!--*-nxml-*--> |
2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" | |
3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> | |
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_get_data"> | |
25 | ||
26 | <refentryinfo> | |
27 | <title>sd_journal_get_data</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_get_data</refentrytitle> | |
42 | <manvolnum>3</manvolnum> | |
43 | </refmeta> | |
44 | ||
45 | <refnamediv> | |
46 | <refname>sd_journal_get_data</refname> | |
47 | <refname>sd_journal_enumerate_data</refname> | |
48 | <refname>sd_journal_restart_data</refname> | |
49 | <refname>SD_JOURNAL_FOREACH_DATA</refname> | |
50 | <refpurpose>Read data fields from the current journal entry</refpurpose> | |
51 | </refnamediv> | |
52 | ||
53 | <refsynopsisdiv> | |
54 | <funcsynopsis> | |
55 | <funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo> | |
56 | ||
57 | <funcprototype> | |
58 | <funcdef>int <function>sd_journal_get_data</function></funcdef> | |
59 | <paramdef>sd_journal* <parameter>j</parameter></paramdef> | |
60 | <paramdef>const char* <parameter>field</parameter></paramdef> | |
61 | <paramdef>const void** <parameter>data</parameter></paramdef> | |
62 | <paramdef>size_t* <parameter>length</parameter></paramdef> | |
63 | </funcprototype> | |
64 | ||
65 | <funcprototype> | |
66 | <funcdef>int <function>sd_journal_enumerate_data</function></funcdef> | |
67 | <paramdef>sd_journal* <parameter>j</parameter></paramdef> | |
68 | <paramdef>const void** <parameter>data</parameter></paramdef> | |
69 | <paramdef>size_t* <parameter>length</parameter></paramdef> | |
70 | </funcprototype> | |
71 | ||
72 | <funcprototype> | |
73 | <funcdef>int <function>sd_journal_restart_data</function></funcdef> | |
74 | <paramdef>sd_journal* <parameter>j</parameter></paramdef> | |
75 | </funcprototype> | |
76 | ||
77 | <funcprototype> | |
78 | <funcdef><function>SD_JOURNAL_FOREACH_DATA</function></funcdef> | |
79 | <paramdef>sd_journal* <parameter>j</parameter></paramdef> | |
80 | <paramdef>const void* <parameter>data</parameter></paramdef> | |
81 | <paramdef>size_t <parameter>length</parameter></paramdef> | |
82 | </funcprototype> | |
83 | ||
84 | </funcsynopsis> | |
85 | </refsynopsisdiv> | |
86 | ||
87 | <refsect1> | |
88 | <title>Description</title> | |
89 | ||
90 | <para><function>sd_journal_get_data()</function> gets | |
91 | the data object associated with a specific field from | |
92 | the current journal entry. It takes four arguments: | |
93 | the journal context object, a string with the field | |
94 | name to request, plus a pair of pointers to | |
95 | pointer/size variables where the data object and its | |
96 | size shall be stored in. The field name should be an | |
97 | entry field name. Well-known field names are listed in | |
98 | <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>. The | |
99 | returned data is in a read-only memory map and is only | |
100 | valid until the next invocation of | |
101 | <function>sd_journal_get_data()</function> or | |
102 | <function>sd_journal_enumerate_data()</function>, or | |
103 | the read pointer is altered. Note that the data | |
104 | returned will be prefixed with the field name and | |
105 | '='.</para> | |
106 | ||
107 | <para><function>sd_journal_enumerate_data()</function> | |
108 | may be used to iterate through all fields of the | |
109 | current entry. On each invocation the data for the | |
110 | next field is returned. The order of these fields is | |
111 | not defined. The data returned is in the same format | |
112 | as with <function>sd_journal_get_data()</function> and | |
113 | also follows the same life-time semantics.</para> | |
114 | ||
115 | <para><function>sd_journal_restart_data()</function> | |
116 | resets the data enumeration index to the beginning of | |
117 | the entry. The next invocation of | |
118 | <function>sd_journal_enumerate_data()</function> will return the first | |
119 | field of the entry again.</para> | |
120 | ||
121 | <para>Note that the | |
122 | <function>SD_JOURNAL_FOREACH_DATA()</function> macro | |
123 | may be used as a wrapper around | |
124 | <function>sd_journal_restart_data()</function> and | |
125 | <function>sd_journal_enumerate_data()</function>.</para> | |
126 | ||
127 | <para>Note that these functions will not work before | |
128 | <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
7a8a6e88 | 129 | (or related call) has been called at least |
4a010f4e | 130 | once, in order to position the read pointer at a valid entry.</para> |
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131 | </refsect1> |
132 | ||
133 | <refsect1> | |
134 | <title>Return Value</title> | |
135 | ||
136 | <para><function>sd_journal_get_data()</function> | |
137 | returns 0 on success or a negative errno-style error | |
138 | code. If the current entry does not include the | |
139 | specified field -ENOENT is returned. If | |
140 | <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
141 | has not been called at least once -EADDRNOTAVAIL is | |
142 | returned. <function>sd_journal_enumerate_data()</function> | |
143 | returns a positive integer if the next field has been | |
144 | read, 0 when no more fields are known, or a negative | |
145 | errno-style error | |
146 | code. <function>sd_journal_restart_data()</function> | |
147 | returns nothing.</para> | |
148 | </refsect1> | |
149 | ||
150 | <refsect1> | |
151 | <title>Notes</title> | |
152 | ||
153 | <para>The <function>sd_journal_get_data()</function>, | |
154 | <function>sd_journal_enumerate_data()</function> and | |
155 | <function>sd_journal_restart_data()</function> | |
156 | interfaces are available as shared library, which can | |
157 | be compiled and linked to with the | |
158 | <literal>libsystemd-journal</literal> | |
159 | <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> | |
160 | file.</para> | |
161 | </refsect1> | |
162 | ||
163 | <refsect1> | |
164 | <title>Examples</title> | |
165 | ||
166 | <para>See | |
167 | <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
168 | for a complete example how to use | |
169 | <function>sd_journal_get_data()</function>.</para> | |
170 | ||
171 | <para>Use the | |
172 | <function>SD_JOURNAL_FOREACH_DATA</function> macro to | |
173 | iterate through all fields of the current journal | |
174 | entry:</para> | |
175 | ||
176 | <programlisting>... | |
177 | int print_fields(sd_journal *j) { | |
178 | const void *data; | |
179 | size_t l; | |
180 | SD_JOURNAL_FOREACH_DATA(j, data, length) | |
181 | printf("%.*s\n", (int) length, data); | |
182 | } | |
183 | ...</programlisting> | |
184 | ||
185 | </refsect1> | |
186 | ||
187 | <refsect1> | |
188 | <title>See Also</title> | |
189 | ||
190 | <para> | |
191 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
192 | <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>, | |
193 | <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
194 | <citerefentry><refentrytitle>sd_journal_open</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
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195 | <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
196 | <citerefentry><refentrytitle>sd_journal_get_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
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197 | </para> |
198 | </refsect1> | |
199 | ||
200 | </refentry> |