4.3BSD - /usr/man/cat2/adjtime.0

ADJTIME(2)                                                          ADJTIME(2)


NAME
       adjtime - correct the time to allow synchronization of the system clock

SYNOPSIS
       #include <sys/time.h>

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

DESCRIPTION
       Adjtime makes small adjustments to the system time, as returned by get���
       timeofday(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 com‐
       plete.  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-zero, then the struc‐
       ture  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 super-user.

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
       The following error codes may be set in errno:

       [EFAULT]       An  argument  points  outside  the  process’s  allocated
                      address space.

       [EPERM]        The process’s effective user  ID  is  not  that  of  the
                      super-user.

SEE ALSO
       date(1), gettimeofday(2), timed(8), timedc(8),
       TSP:  The Time Synchronization Protocol for UNIX 4.3BSD, R. Gusella and
       S. Zatti


4.3 Berkeley Distribution        May 15, 1986                       ADJTIME(2)