adjtime(2)                                             adjtime(2)



     NAME
          adjtime - correct the system time

     SYNOPSIS
          #include <sys/time.h>

          adjtime(delta, olddelta)
          struct timeval *delta;
          struct timeval *olddelta;

     DESCRIPTION
          adjtime makes small adjustments to the system time, as re-
          turned 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 posi-
          tive, 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 increas-
          ing function.  A time correction from an earlier call to
          adjtime may not be finished when adjtime is called again.
          If olddelta is nonzero, then 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(2) is restricted to the superuser.

     RETURN VALUE
          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
          errno.

     ERRORS
          adjtime will fail if:

          [EFAULT]       An argument points outside the process's al-
                         located address space.

          [EPERM]        The process's effective user ID is not that
                         of the superuser.

     SEE ALSO
          date(1).





     April, 1990                                                     1