leapsecs(3)leapsecs(3)NAMEleapsecs - 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-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
/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 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 ALSOtai(3)leapsecs(3)
