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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 | <!-- | |
572eb058 | 6 | SPDX-License-Identifier: LGPL-2.1+ |
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7 | --> |
8 | ||
7d6b2723 | 9 | <refentry id="sd_journal_add_match" xmlns:xi="http://www.w3.org/2001/XInclude"> |
f4e761c4 | 10 | |
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11 | <refentryinfo> |
12 | <title>sd_journal_add_match</title> | |
13 | <productname>systemd</productname> | |
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14 | </refentryinfo> |
15 | ||
16 | <refmeta> | |
17 | <refentrytitle>sd_journal_add_match</refentrytitle> | |
18 | <manvolnum>3</manvolnum> | |
19 | </refmeta> | |
20 | ||
21 | <refnamediv> | |
22 | <refname>sd_journal_add_match</refname> | |
23 | <refname>sd_journal_add_disjunction</refname> | |
24 | <refname>sd_journal_add_conjunction</refname> | |
25 | <refname>sd_journal_flush_matches</refname> | |
26 | <refpurpose>Add or remove entry matches</refpurpose> | |
27 | </refnamediv> | |
28 | ||
29 | <refsynopsisdiv> | |
30 | <funcsynopsis> | |
31 | <funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo> | |
32 | ||
33 | <funcprototype> | |
34 | <funcdef>int <function>sd_journal_add_match</function></funcdef> | |
35 | <paramdef>sd_journal *<parameter>j</parameter></paramdef> | |
36 | <paramdef>const void *<parameter>data</parameter></paramdef> | |
37 | <paramdef>size_t <parameter>size</parameter></paramdef> | |
38 | </funcprototype> | |
39 | ||
40 | <funcprototype> | |
41 | <funcdef>int <function>sd_journal_add_disjunction</function></funcdef> | |
42 | <paramdef>sd_journal *<parameter>j</parameter></paramdef> | |
43 | </funcprototype> | |
44 | ||
45 | <funcprototype> | |
46 | <funcdef>int <function>sd_journal_add_conjunction</function></funcdef> | |
47 | <paramdef>sd_journal *<parameter>j</parameter></paramdef> | |
48 | </funcprototype> | |
49 | ||
50 | <funcprototype> | |
51 | <funcdef>void <function>sd_journal_flush_matches</function></funcdef> | |
52 | <paramdef>sd_journal *<parameter>j</parameter></paramdef> | |
53 | </funcprototype> | |
54 | </funcsynopsis> | |
55 | </refsynopsisdiv> | |
56 | ||
57 | <refsect1> | |
58 | <title>Description</title> | |
59 | ||
60 | <para><function>sd_journal_add_match()</function> adds a match by | |
61 | which to filter the entries of the journal file. Matches applied | |
62 | with this call will filter what can be iterated through and read | |
63 | from the journal file via calls like | |
64 | <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
65 | and | |
66 | <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>. | |
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67 | Parameter <parameter>data</parameter> must be of the form |
68 | <literal><replaceable>FIELD</replaceable>=<replaceable>value</replaceable></literal>, | |
69 | where the <replaceable>FIELD</replaceable> part is a short uppercase string consisting only | |
70 | of 0–9, A–Z and the underscore; it may not begin with two underscores or be the empty | |
71 | string. The <replaceable>value</replaceable> part may be anything, including binary. Parameter | |
72 | <parameter>size</parameter> specifies the number of bytes in <parameter>data</parameter> | |
73 | (i.e. the length of <replaceable>FIELD</replaceable>, plus one, plus the length of | |
74 | <replaceable>value</replaceable>). Parameter <parameter>size</parameter> may also be | |
75 | specified as <constant>0</constant>, in which case <parameter>data</parameter> | |
76 | must be a <constant>NUL</constant>-terminated string, and the bytes before the terminating | |
77 | zero are used as the match.</para> | |
78 | ||
79 | <para>If a match is applied, only entries with this field set | |
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80 | will be iterated. Multiple matches may be active at the same time: |
81 | If they apply to different fields, only entries with both fields | |
82 | set like this will be iterated. If they apply to the same fields, | |
83 | only entries where the field takes one of the specified values | |
84 | will be iterated. Well known fields are documented in | |
85 | <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>. | |
86 | Whenever a new match is added the current entry position is reset, | |
87 | and | |
88 | <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
89 | (or a similar call) needs to be called before entries can be read | |
90 | again.</para> | |
91 | ||
92 | <para><function>sd_journal_add_disjunction()</function> may be | |
93 | used to insert a disjunction (i.e. logical OR) in the match list. | |
94 | If this call is invoked, all previously added matches since the | |
95 | last invocation of | |
96 | <function>sd_journal_add_disjunction()</function> or | |
97 | <function>sd_journal_add_conjunction()</function> are combined in | |
98 | an OR with all matches added afterwards, until | |
99 | <function>sd_journal_add_disjunction()</function> or | |
100 | <function>sd_journal_add_conjunction()</function> is invoked again | |
101 | to begin the next OR or AND term. </para> | |
102 | ||
103 | <para><function>sd_journal_add_conjunction()</function> may be | |
104 | used to insert a conjunction (i.e. logical AND) in the match list. | |
105 | If this call is invoked, all previously added matches since the | |
106 | last invocation of | |
107 | <function>sd_journal_add_conjunction()</function> are combined in | |
108 | an AND with all matches added afterwards, until | |
109 | <function>sd_journal_add_conjunction()</function> is invoked again | |
110 | to begin the next AND term. The combination of | |
111 | <function>sd_journal_add_match()</function>, | |
112 | <function>sd_journal_add_disjunction()</function> and | |
113 | <function>sd_journal_add_conjunction()</function> may be used to | |
114 | build complex search terms, even though full logical expressions | |
115 | are not available. Note that | |
116 | <function>sd_journal_add_conjunction()</function> operates one | |
117 | level 'higher' than | |
118 | <function>sd_journal_add_disjunction()</function>. It is hence | |
119 | possible to build an expression of AND terms, consisting of OR | |
120 | terms, consisting of AND terms, consisting of OR terms of matches | |
121 | (the latter OR expression is implicitly created for matches with | |
122 | the same field name, see above).</para> | |
123 | ||
124 | <para><function>sd_journal_flush_matches()</function> may be used | |
125 | to flush all matches, disjunction and conjunction terms again. | |
126 | After this call all filtering is removed and all entries in the | |
127 | journal will be iterated again.</para> | |
128 | ||
129 | <para>Note that filtering via matches only applies to the way the | |
130 | journal is read, it has no effect on storage on disk.</para> | |
131 | </refsect1> | |
132 | ||
133 | <refsect1> | |
134 | <title>Return Value</title> | |
135 | ||
136 | <para><function>sd_journal_add_match()</function>, | |
137 | <function>sd_journal_add_disjunction()</function> and | |
138 | <function>sd_journal_add_conjunction()</function> | |
139 | return 0 on success or a negative errno-style error | |
140 | code. <function>sd_journal_flush_matches()</function> | |
141 | returns nothing.</para> | |
142 | </refsect1> | |
143 | ||
7d6b2723 | 144 | <xi:include href="libsystemd-pkgconfig.xml" /> |
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145 | |
146 | <refsect1> | |
147 | <title>Examples</title> | |
148 | ||
149 | <para>The following example adds matches to a journal context | |
150 | object to iterate only through messages generated by the Avahi | |
151 | service at the four error log levels, plus all messages of the | |
152 | message ID 03bb1dab98ab4ecfbf6fff2738bdd964 coming from any | |
153 | service (this example lacks the necessary error checking):</para> | |
154 | ||
1eecafb8 | 155 | <programlisting>… |
f4e761c4 | 156 | int add_matches(sd_journal *j) { |
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157 | sd_journal_add_match(j, "_SYSTEMD_UNIT=avahi-daemon.service", 0); |
158 | sd_journal_add_match(j, "PRIORITY=0", 0); | |
159 | sd_journal_add_match(j, "PRIORITY=1", 0); | |
160 | sd_journal_add_match(j, "PRIORITY=2", 0); | |
161 | sd_journal_add_match(j, "PRIORITY=3", 0); | |
162 | sd_journal_add_disjunction(j); | |
163 | sd_journal_add_match(j, "MESSAGE_ID=03bb1dab98ab4ecfbf6fff2738bdd964", 0); | |
f4e761c4 | 164 | }</programlisting> |
798d3a52 | 165 | </refsect1> |
f4e761c4 | 166 | |
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167 | <refsect1> |
168 | <title>See Also</title> | |
f4e761c4 | 169 | |
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170 | <para> |
171 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
172 | <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
173 | <citerefentry><refentrytitle>sd_journal_open</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
174 | <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
175 | <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
176 | <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry> | |
177 | </para> | |
178 | </refsect1> | |
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179 | |
180 | </refentry> |