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
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.
is not a null pointer,
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.
is restricted to the super-user.