sd_journal_flush_matches (3) - Linux Manuals
sd_journal_flush_matches: Add or remove entry matches
NAME
sd_journal_add_match, sd_journal_add_disjunction, sd_journal_add_conjunction, sd_journal_flush_matches - Add or remove entry matches
SYNOPSIS
#include <systemd/sd-journal.h>
-
int sd_journal_add_match(sd_journal
* j, const void* data, size_tsize); -
int sd_journal_add_disjunction(sd_journal
* j); -
int sd_journal_add_conjunction(sd_journal
* j); -
void sd_journal_flush_matches(sd_journal
* j);
DESCRIPTION
sd_journal_add_match()
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.
RETURN VALUE
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.
NOTES
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
EXAMPLES
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); }
SEE ALSO
systemd(1), sd-journal(3), sd_journal_open(3), sd_journal_next(3), sd_journal_get_data(3), systemd.journal-fields(7)