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.
is null, no adjustment is done.
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.
Only the superuser may adjust the time using the
A return value of 0 indicates that the call succeeded.
A return value of \-1 indicates that an error occurred, and in this
case an error code is stored in the global variable
will fail if:
Either of the arguments point outside the process's allocated address space.
argument is non-null and the process's effective user ID is not that
of the superuser.