|
NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | EXAMPLES | SEE ALSO | COLOPHON |
SD_JOURNAL_ADD_MATCH(3) sd_journal_add_match SD_JOURNAL_ADD_MATCH(3)
sd_journal_add_match, sd_journal_add_disjunction,
sd_journal_add_conjunction, sd_journal_flush_matches - Add or remove
entry matches
#include <systemd/sd-journal.h>
int sd_journal_add_match(sd_journal *j, const void *data,
size_t size);
int sd_journal_add_disjunction(sd_journal *j);
int sd_journal_add_conjunction(sd_journal *j);
void sd_journal_flush_matches(sd_journal *j);
sd_journal_add_match() adds a match by which to filter the entries of
the journal file. Matches applied with this call will filter what can
be iterated through and read from the journal file via calls like
sd_journal_next(3) and sd_journal_get_data(3). Parameter data must be
of the form "FIELD=value", where the FIELD part is a short uppercase
string consisting only of 0–9, A–Z and the underscore; it may not
begin with two underscores or be the empty string. The value part may
be anything, including binary. Parameter size specifies the number of
bytes in data (i.e. the length of FIELD, plus one, plus the length of
value). Parameter size may also be specified as 0, in which case data
must be a NUL-terminated string, and the bytes before the terminating
zero are used as the match.
If a match is applied, only entries with this field set will be
iterated. Multiple matches may be active at the same time: If they
apply to different fields, only entries with both fields set like
this will be iterated. If they apply to the same fields, only entries
where the field takes one of the specified values will be iterated.
Well known fields are documented in systemd.journal-fields(7).
Whenever a new match is added the current entry position is reset,
and sd_journal_next(3) (or a similar call) needs to be called before
entries can be read again.
sd_journal_add_disjunction() may be used to insert a disjunction
(i.e. logical OR) in the match list. If this call is invoked, all
previously added matches since the last invocation of
sd_journal_add_disjunction() or sd_journal_add_conjunction() are
combined in an OR with all matches added afterwards, until
sd_journal_add_disjunction() or sd_journal_add_conjunction() is
invoked again to begin the next OR or AND term.
sd_journal_add_conjunction() may be used to insert a conjunction
(i.e. logical AND) in the match list. If this call is invoked, all
previously added matches since the last invocation of
sd_journal_add_conjunction() are combined in an AND with all matches
added afterwards, until sd_journal_add_conjunction() is invoked again
to begin the next AND term. The combination of
sd_journal_add_match(), sd_journal_add_disjunction() and
sd_journal_add_conjunction() may be used to build complex search
terms, even though full logical expressions are not available. Note
that sd_journal_add_conjunction() operates one level 'higher' than
sd_journal_add_disjunction(). It is hence possible to build an
expression of AND terms, consisting of OR terms, consisting of AND
terms, consisting of OR terms of matches (the latter OR expression is
implicitly created for matches with the same field name, see above).
sd_journal_flush_matches() may be used to flush all matches,
disjunction and conjunction terms again. After this call all
filtering is removed and all entries in the journal will be iterated
again.
Note that filtering via matches only applies to the way the journal
is read, it has no effect on storage on disk.
sd_journal_add_match(), sd_journal_add_disjunction() and
sd_journal_add_conjunction() return 0 on success or a negative
errno-style error code. sd_journal_flush_matches() returns nothing.
All functions listed here are thread-agnostic and only a single
thread may operate on a given sd_journal object.
The sd_journal_add_match(), sd_journal_add_disjunction(),
sd_journal_add_conjunction() and sd_journal_flush_matches()
interfaces are available as a shared library, which can be compiled
and linked to with the libsystemd pkg-config(1) file.
The following example adds matches to a journal context object to
iterate only through messages generated by the Avahi service at the
four error log levels, plus all messages of the message ID
03bb1dab98ab4ecfbf6fff2738bdd964 coming from any service (this
example lacks the necessary error checking):
...
int add_matches(sd_journal *j) {
sd_journal_add_match(j, "_SYSTEMD_UNIT=avahi-daemon.service", 0);
sd_journal_add_match(j, "PRIORITY=0", 0);
sd_journal_add_match(j, "PRIORITY=1", 0);
sd_journal_add_match(j, "PRIORITY=2", 0);
sd_journal_add_match(j, "PRIORITY=3", 0);
sd_journal_add_disjunction(j);
sd_journal_add_match(j, "MESSAGE_ID=03bb1dab98ab4ecfbf6fff2738bdd964", 0);
}
systemd(1), sd-journal(3), sd_journal_open(3), sd_journal_next(3),
sd_journal_get_data(3), systemd.journal-fields(7)
This page is part of the systemd (systemd system and service manager)
project. Information about the project can be found at
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report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩. This
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COLOPHON (which is not part of the original manual page), send a mail
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systemd 234 SD_JOURNAL_ADD_MATCH(3)
Pages that refer to this page: sd-journal(3), sd_journal_enumerate_fields(3), sd_journal_query_unique(3), systemd.directives(7), systemd.index(7), systemd.journal-fields(7)