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1a2be33a | 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+ --> |
1a2be33a | 5 | |
7d6b2723 | 6 | <refentry id="sd_journal_query_unique" xmlns:xi="http://www.w3.org/2001/XInclude"> |
1a2be33a | 7 | |
798d3a52 ZJS |
8 | <refentryinfo> |
9 | <title>sd_journal_query_unique</title> | |
10 | <productname>systemd</productname> | |
798d3a52 ZJS |
11 | </refentryinfo> |
12 | ||
13 | <refmeta> | |
14 | <refentrytitle>sd_journal_query_unique</refentrytitle> | |
15 | <manvolnum>3</manvolnum> | |
16 | </refmeta> | |
17 | ||
18 | <refnamediv> | |
19 | <refname>sd_journal_query_unique</refname> | |
20 | <refname>sd_journal_enumerate_unique</refname> | |
0da322d9 | 21 | <refname>sd_journal_enumerate_available_unique</refname> |
798d3a52 ZJS |
22 | <refname>sd_journal_restart_unique</refname> |
23 | <refname>SD_JOURNAL_FOREACH_UNIQUE</refname> | |
24 | <refpurpose>Read unique data fields from the journal</refpurpose> | |
25 | </refnamediv> | |
26 | ||
27 | <refsynopsisdiv> | |
28 | <funcsynopsis> | |
29 | <funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo> | |
30 | ||
31 | <funcprototype> | |
32 | <funcdef>int <function>sd_journal_query_unique</function></funcdef> | |
33 | <paramdef>sd_journal *<parameter>j</parameter></paramdef> | |
34 | <paramdef>const char *<parameter>field</parameter></paramdef> | |
35 | </funcprototype> | |
36 | ||
0da322d9 ZJS |
37 | <funcprototype> |
38 | <funcdef>int <function>sd_journal_enumerate_available_unique</function></funcdef> | |
39 | <paramdef>sd_journal *<parameter>j</parameter></paramdef> | |
40 | <paramdef>const void **<parameter>data</parameter></paramdef> | |
41 | <paramdef>size_t *<parameter>length</parameter></paramdef> | |
42 | </funcprototype> | |
43 | ||
798d3a52 ZJS |
44 | <funcprototype> |
45 | <funcdef>int <function>sd_journal_enumerate_unique</function></funcdef> | |
46 | <paramdef>sd_journal *<parameter>j</parameter></paramdef> | |
47 | <paramdef>const void **<parameter>data</parameter></paramdef> | |
48 | <paramdef>size_t *<parameter>length</parameter></paramdef> | |
49 | </funcprototype> | |
50 | ||
51 | <funcprototype> | |
52 | <funcdef>void <function>sd_journal_restart_unique</function></funcdef> | |
53 | <paramdef>sd_journal *<parameter>j</parameter></paramdef> | |
54 | </funcprototype> | |
55 | ||
56 | <funcprototype> | |
57 | <funcdef><function>SD_JOURNAL_FOREACH_UNIQUE</function></funcdef> | |
58 | <paramdef>sd_journal *<parameter>j</parameter></paramdef> | |
59 | <paramdef>const void *<parameter>data</parameter></paramdef> | |
60 | <paramdef>size_t <parameter>length</parameter></paramdef> | |
61 | </funcprototype> | |
62 | ||
63 | </funcsynopsis> | |
64 | </refsynopsisdiv> | |
65 | ||
66 | <refsect1> | |
67 | <title>Description</title> | |
68 | ||
0da322d9 ZJS |
69 | <para><function>sd_journal_query_unique()</function> queries the journal for all unique values the |
70 | specified field can take. It takes two arguments: the journal to query and the field name to look | |
71 | for. Well-known field names are listed on | |
72 | <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>, | |
73 | but any field can be specified. Field names must be specified without a trailing | |
74 | <literal>=</literal>. After this function has been executed successfully the field values may be queried | |
75 | using <function>sd_journal_enumerate_unique()</function> and | |
76 | <function>sd_journal_enumerate_available_unique()</function>. Invoking one of those calls will change the | |
77 | field name being queried and reset the enumeration index to the first field value that matches.</para> | |
78 | ||
79 | <para><function>sd_journal_enumerate_unique()</function> may be used to iterate through all data fields | |
80 | which match the previously selected field name as set with | |
81 | <function>sd_journal_query_unique()</function>. On each invocation the next field data matching the field | |
82 | name is returned. The order of the returned data fields is not defined. It takes three arguments: the | |
83 | journal object, plus a pair of pointers to pointer/size variables where the data object and its size | |
84 | shall be stored. The returned data is in a read-only memory map and is only valid until the next | |
85 | invocation of <function>sd_journal_enumerate_unique()</function>. Note that the data returned will be | |
86 | prefixed with the field name and <literal>=</literal>. Note that this call is subject to the data field | |
87 | size threshold as controlled by <function>sd_journal_set_data_threshold()</function> and only the initial | |
88 | part of the field up to the threshold is returned. An error is returned for fields which cannot be | |
89 | retrieved. See the error list below for details.</para> | |
90 | ||
91 | <para><function>sd_journal_enumerate_available_unique()</function> is similar to | |
92 | <function>sd_journal_enumerate_unique()</function>, but silently skips any fields which may be valid, but | |
93 | are too large or not supported by current implementation.</para> | |
798d3a52 ZJS |
94 | |
95 | <para><function>sd_journal_restart_unique()</function> resets the | |
96 | data enumeration index to the beginning of the list. The next | |
97 | invocation of <function>sd_journal_enumerate_unique()</function> | |
98 | will return the first field data matching the field name | |
99 | again.</para> | |
100 | ||
0da322d9 ZJS |
101 | <para>Note that the <function>SD_JOURNAL_FOREACH_UNIQUE()</function> macro may be used as a handy wrapper |
102 | around <function>sd_journal_restart_unique()</function> and | |
103 | <function>sd_journal_enumerate_available_unique()</function>.</para> | |
798d3a52 ZJS |
104 | |
105 | <para>Note that these functions currently are not influenced by | |
106 | matches set with <function>sd_journal_add_match()</function> but | |
107 | this might change in a later version of this software.</para> | |
eb86030e LP |
108 | |
109 | <para>To enumerate all field names currently in use (and thus all suitable field parameters for | |
110 | <function>sd_journal_query_unique()</function>), use the | |
111 | <citerefentry><refentrytitle>sd_journal_enumerate_fields</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
112 | call.</para> | |
798d3a52 ZJS |
113 | </refsect1> |
114 | ||
115 | <refsect1> | |
116 | <title>Return Value</title> | |
117 | ||
0da322d9 ZJS |
118 | <para><function>sd_journal_query_unique()</function> returns 0 on success or a negative errno-style error |
119 | code. <function>sd_journal_enumerate_unique()</function> and and | |
120 | <function>sd_journal_query_available_unique()</function> return a positive integer if the next field data | |
121 | has been read, 0 when no more fields remain, or a negative errno-style error code. | |
122 | <function>sd_journal_restart_unique()</function> doesn't return anything.</para> | |
123 | ||
124 | <refsect2> | |
125 | <title>Errors</title> | |
126 | ||
127 | <para>Returned errors may indicate the following problems:</para> | |
128 | ||
129 | <variablelist> | |
130 | <xi:include href="sd_journal_get_data.xml" xpointer="EINVAL"/> | |
131 | <xi:include href="sd_journal_get_data.xml" xpointer="ECHILD"/> | |
132 | <xi:include href="sd_journal_get_data.xml" xpointer="EADDRNOTAVAIL"/> | |
133 | <xi:include href="sd_journal_get_data.xml" xpointer="ENOENT"/> | |
134 | <xi:include href="sd_journal_get_data.xml" xpointer="ENOBUFS"/> | |
135 | <xi:include href="sd_journal_get_data.xml" xpointer="E2BIG"/> | |
136 | <xi:include href="sd_journal_get_data.xml" xpointer="EPROTONOSUPPORT"/> | |
137 | <xi:include href="sd_journal_get_data.xml" xpointer="EBADMSG"/> | |
138 | <xi:include href="sd_journal_get_data.xml" xpointer="EIO"/> | |
139 | </variablelist> | |
140 | </refsect2> | |
798d3a52 ZJS |
141 | </refsect1> |
142 | ||
143 | <refsect1> | |
144 | <title>Notes</title> | |
145 | ||
64a7ef8b | 146 | <xi:include href="threads-aware.xml" xpointer="strict"/> |
a8d46a16 | 147 | |
7d6b2723 | 148 | <xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/> |
798d3a52 ZJS |
149 | </refsect1> |
150 | ||
151 | <refsect1> | |
152 | <title>Examples</title> | |
153 | ||
0da322d9 ZJS |
154 | <para>Use the <function>SD_JOURNAL_FOREACH_UNIQUE</function> macro to iterate through all values a field |
155 | of the journal can take (and which can be accessed on the given architecture and are not compressed with | |
156 | an unsupported mechanism). The following example lists all unit names referenced in the journal:</para> | |
798d3a52 | 157 | |
787f78b6 | 158 | <programlisting><xi:include href="journal-iterate-unique.c" parse="text" /></programlisting> |
798d3a52 | 159 | </refsect1> |
1a2be33a | 160 | |
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161 | <refsect1> |
162 | <title>See Also</title> | |
1a2be33a | 163 | |
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164 | <para> |
165 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
166 | <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>, | |
167 | <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
168 | <citerefentry><refentrytitle>sd_journal_open</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
eb86030e | 169 | <citerefentry><refentrytitle>sd_journal_enumerate_fields</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
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170 | <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
171 | <citerefentry><refentrytitle>sd_journal_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
172 | </para> | |
173 | </refsect1> | |
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174 | |
175 | </refentry> |