adjtime(2)                SYSTEM CALLS                 adjtime(2)



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

SYNOPSIS
     #include <sys/time.h>

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

DESCRIPTION
     adjtime adjusts the system's notion of the current time,  as
     returned  by  gettimeofday(3C), advancing or retarding it by
     the amount of time specified in the struct  timeval  pointed
     to by delta.

     The adjustment is effected by speeding up (if that amount of
     time is positive) or slowing down (if that amount of time is
     negative) the system's clock by some small percentage,  gen-
     erally  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 delta is 0, then olddelta  returns  the
     status of the effects of the previous adjtime call and there
     is no effect on the time correction  as  a  result  of  this
     call.  If olddelta is not a NULL pointer, then the structure
     it points to  will  contain,  upon  return,  the  number  of
     seconds  and/or  microseconds still to be corrected from the
     earlier  call.   If  olddelta  is  a   NULL   pointer,   the
     corresponding information will not be returned.

     This call may be used in 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 super-user may adjust the time of day.

     The adjustment value will be silently rounded to the resolu-
     tion of the system clock.

RETURN
     A 0 return value indicates that the call  succeeded.   A  -1
     return  value  indicates an error occurred, and in this case
     an error code is stored into the global variable errno.

ERRORS
     The following error codes may be set in errno:

     EFAULT              delta or  olddelta  points  outside  the
                         process's  allocated  address  space, or
                         olddelta  points  to  a  region  of  the



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adjtime(2)                SYSTEM CALLS                 adjtime(2)



                         process' allocated address space that is
                         not writable.

     EPERM               The process's effective user ID  is  not
                         that of the super-user.

SEE ALSO
     gettimeofday(3C)
     date(1) in the User's Reference Manual.














































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