DragonFly On-Line Manual Pages
ADJTIME(2) DragonFly System Calls Manual ADJTIME(2)
adjtime - correct the time to allow synchronization of the system clock
Standard C Library (libc, -lc)
adjtime(const struct timeval *delta, struct timeval *olddelta);
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 olddelta is non-NULL, the structure
pointed to will contain, upon return, the number of microseconds still to
be corrected from the earlier call.
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.
The call adjtime() is restricted to the super-user.
The adjtime() function returns the value 0 if successful; otherwise the
value -1 is returned and the global variable errno is set to indicate the
Adjtime() will fail if:
[EFAULT] An argument points outside the process's allocated
[EPERM] The process's effective user ID is not that of the
The adjtime() function call appeared in 4.3BSD.
DragonFly 5.5-DEVELOPMENT June 17, 2019 DragonFly 5.5-DEVELOPMENT