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leapsecs(3)           DragonFly Library Functions Manual           leapsecs(3)

NAME
       leapsecs - handle UTC leap seconds

SYNTAX
       #include <leapsecs.h>

       int leapsecs_sub(&t);
       void leapsecs_add(&t,hit);

       int leapsecs_read();
       int leapsecs_init();

       struct tai t;
       int hit;

DESCRIPTION
       leapsecs_sub changes a seconds-since-epoch count into a non-leap-
       seconds-since-epoch count.  It interprets t as a TAI64 label, subtracts
       from t the number of leap seconds that have occurred before or at t,
       and places the result back into t.

       leapsecs_sub returns 1 if t was a leap second, 0 otherwise.

       leapsecs_add reverses the effect of leapsecs_sub.  hit must be 1 for a
       leap second, 0 otherwise.

LEAP-SECOND TABLE
       The current implementation of leapsecs_sub and leapsecs_add uses a
       leap-second table read from disk.

       leapsecs_read reads the leap-second table from
       /usr/local/etc/leapsecs.dat.  It returns 0 on success, -1 on error.  If
       /usr/local/etc/leapsecs.dat does not exist, leapsecs_read treats it as
       an empty file.

       leapsecs_init is a one-time version of leapsecs_read.  Initially it is
       the same as leapsecs_read; however, once leapsecs_read returns 0,
       leapsecs_init will always return 0 without calling leapsecs_read again.

       leapsecs_add and leapsecs_sub call leapsecs_init.  WARNING: If
       leapsecs_init returns failure, leapsecs_add and leapsecs_sub will
       proceed without a leap-second table.  For reliability, all programs
       should call leapsecs_init at startup and check for errors.

       WARNING: New entries are added to the leap-second table on disk every
       12 to 18 months.  leapsecs_read may be called repeatedly.  It leaves
       the old table alone on error.  For reliability, all long-running
       programs should call leapsecs_read at least once every month.

SEE ALSO
       tai(3)

                                                                   leapsecs(3)