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-sec-
       onds-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  /etc/leapsecs.dat.   It
       returns  0  on  success,  -1  on  error.  If /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  pro-
       ceed 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  pro-
       grams should call leapsecs_read at least once every month.

SEE ALSO

       tai(3)



                                                                   leapsecs(3)