1SD_JOURNAL_ADD_MATCH(3)      sd_journal_add_match      SD_JOURNAL_ADD_MATCH(3)
2
3
4

NAME

6       sd_journal_add_match, sd_journal_add_disjunction,
7       sd_journal_add_conjunction, sd_journal_flush_matches - Add or remove
8       entry matches
9

SYNOPSIS

11       #include <systemd/sd-journal.h>
12
13       int sd_journal_add_match(sd_journal *j, const void *data, size_t size);
14
15       int sd_journal_add_disjunction(sd_journal *j);
16
17       int sd_journal_add_conjunction(sd_journal *j);
18
19       void sd_journal_flush_matches(sd_journal *j);
20

DESCRIPTION

22       sd_journal_add_match() adds a match by which to filter the entries of
23       the journal file. Matches applied with this call will filter what can
24       be iterated through and read from the journal file via calls like
25       sd_journal_next(3) and sd_journal_get_data(3). Matches are of the form
26       "FIELD=value", where the field part is a short uppercase string
27       consisting only of 0-9, A-Z and the underscore. It may not begin with
28       two underscores or be the empty string. The value part may be any
29       value, including binary. If a match is applied, only entries with this
30       field set will be iterated. Multiple matches may be active at the same
31       time: If they apply to different fields, only entries with both fields
32       set like this will be iterated. If they apply to the same fields, only
33       entries where the field takes one of the specified values will be
34       iterated. Well known fields are documented in systemd.journal-
35       fields(7). Whenever a new match is added the current entry position is
36       reset, and sd_journal_next(3) (or a similar call) needs to be called
37       before entries can be read again.
38
39       sd_journal_add_disjunction() may be used to insert a disjunction (i.e.
40       logical OR) in the match list. If this call is invoked, all previously
41       added matches since the last invocation of sd_journal_add_disjunction()
42       or sd_journal_add_conjunction() are combined in an OR with all matches
43       added afterwards, until sd_journal_add_disjunction() or
44       sd_journal_add_conjunction() is invoked again to begin the next OR or
45       AND term.
46
47       sd_journal_add_conjunction() may be used to insert a conjunction (i.e.
48       logical AND) in the match list. If this call is invoked, all previously
49       added matches since the last invocation of sd_journal_add_conjunction()
50       are combined in an AND with all matches added afterwards, until
51       sd_journal_add_conjunction() is invoked again to begin the next AND
52       term. The combination of sd_journal_add_match(),
53       sd_journal_add_disjunction() and sd_journal_add_conjunction() may be
54       used to build complex search terms, even though full logical
55       expressions are not available. Note that sd_journal_add_conjunction()
56       operates one level 'higher' than sd_journal_add_disjunction(). It is
57       hence possible to build an expression of AND terms, consisting of OR
58       terms, consisting of AND terms, consisting of OR terms of matches (the
59       latter OR expression is implicitly created for matches with the same
60       field name, see above).
61
62       sd_journal_flush_matches() may be used to flush all matches,
63       disjunction and conjunction terms again. After this call all filtering
64       is removed and all entries in the journal will be iterated again.
65
66       Note that filtering via matches only applies to the way the journal is
67       read, it has no effect on storage on disk.
68

RETURN VALUE

70       sd_journal_add_match(), sd_journal_add_disjunction() and
71       sd_journal_add_conjunction() return 0 on success or a negative
72       errno-style error code.  sd_journal_flush_matches() returns nothing.
73

NOTES

75       The sd_journal_add_match(), sd_journal_add_disjunction(),
76       sd_journal_add_conjunction() and sd_journal_flush_matches() interfaces
77       are available as a shared library, which can be compiled and linked to
78       with the libsystemd pkg-config(1) file.
79

EXAMPLES

81       The following example adds matches to a journal context object to
82       iterate only through messages generated by the Avahi service at the
83       four error log levels, plus all messages of the message ID
84       03bb1dab98ab4ecfbf6fff2738bdd964 coming from any service (this example
85       lacks the necessary error checking):
86
87           ...
88           int add_matches(sd_journal *j) {
89             sd_journal_add_match(j, "_SYSTEMD_UNIT=avahi-daemon.service", 0);
90             sd_journal_add_match(j, "PRIORITY=0", 0);
91             sd_journal_add_match(j, "PRIORITY=1", 0);
92             sd_journal_add_match(j, "PRIORITY=2", 0);
93             sd_journal_add_match(j, "PRIORITY=3", 0);
94             sd_journal_add_disjunction(j);
95             sd_journal_add_match(j, "MESSAGE_ID=03bb1dab98ab4ecfbf6fff2738bdd964", 0);
96           }
97

SEE ALSO

99       systemd(1), sd-journal(3), sd_journal_open(3), sd_journal_next(3),
100       sd_journal_get_data(3), systemd.journal-fields(7)
101
102
103
104systemd 219                                            SD_JOURNAL_ADD_MATCH(3)
Impressum