|ADJTIME(2)||System Calls Manual||ADJTIME(2)|
struct timeval *delta,
adjtime() makes small adjustments to the system time, as returned by gettimeofday(2), advancing or retarding it by the time specified by the timeval delta. If delta is negative, the clock is slowed down by incrementing it more slowly than normal until the correction is complete. If delta is positive, a larger increment than normal is used. The skew used to perform the correction is generally a fraction of one percent. Thus, the time is always a monotonically increasing function. A time correction from an earlier call to
adjtime() may not be finished when
adjtime() is called again. If delta is
NULL, no adjustment is done. If olddelta is non-
NULL, the number of microseconds still to be corrected from the earlier call is stored into *olddelta. Setting the time with settimeofday(2) cancels any in-progress time adjustment.
This call may be used by time servers that synchronize the clocks of computers in a local area network. Such time servers would slow down the clocks of some machines and speed up the clocks of others to bring them to the average network time.
Only the superuser may adjust the time using the
adjtime() will fail if:
NULLand specifies a microsecond value less than zero or greater than or equal to 1 million.
NULLand the process's effective user ID is not that of the superuser.
adjtime() function call appeared in 4.3BSD.
adjtime() to the superuser and might not allow requesting the current correction without specifying a new value.
|January 18, 2019||OpenBSD-current|