correct the time to allow synchronization of the
struct timeval *delta
() makes small adjustments to the
system time, as returned by
advancing or retarding it by the time specified by the timeval
is negative, the clock is slowed down
by incrementing it more slowly than normal until the correction is complete.
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
() may not be finished when
() is called again. If
is null, no adjustment is done. If
is non-null, the structure pointed
to will contain, upon return, the number of microseconds still to be corrected
from the earlier call. Setting the time with
will cancel 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
Only the superuser may adjust the time using the
Upon successful completion, the value 0 is returned; otherwise the
value -1 is returned and the global variable
is set to indicate the error.
() will fail if:
- Either of the arguments point outside the process's allocated address
delta() argument is non-null and
the process's effective user ID is not that of the superuser.
() function call appeared in
Other operating systems restrict calling
to the superuser and might not
allow requesting the current correction without specifying a new value.