SD_JOURNAL_ADD_MATCH(3) 				       sd_journal_add_match					   SD_JOURNAL_ADD_MATCH(3)

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_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);

DESCRIPTION

       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). Matches are 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 any value, including binary. 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.

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-journal pkg-config(1) file.

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)

systemd 208														   SD_JOURNAL_ADD_MATCH(3)