Click this button to go to the index for this section.

adjtime(2)
NAME
  adjtime - Corrects the time to allow synchronization of the system clock

SYNOPSIS
  #include <sys/time.h>
  int adjtime (
	  struct timeval *delta,
	  struct timeval *old_delta );

PARAMETERS
  delta	    Points to the amount of time to be altered.

  old_delta Points to the number of nanoseconds still to be corrected from an
	    earlier call.

DESCRIPTION
  The adjtime() function makes small adjustments to the system time (as
  returned by the gettimer() function), advancing or decreasing it by the
  time specified by the delta parameter of the timeval structure.  If delta
  is negative, the clock is slowed down by incrementing it more slowly than
  normal until the correction is complete.  If delta is positive, a larger
  increment than normal is used until the correction is complete.

  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.  In this case, the delta remaining from the
  original call is replaced by the delta of the current call.  If the
  old_delta parameter is nonzero, then when the adjtime() function returns,
  the structure pointed to will contain the time remaining 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 adjtime() function is restricted to users with superuser privilege.

NOTES
  In BSD, system time is defined in units of seconds and microseconds, while
  in POSIX real time extensions, the units are seconds and nanoseconds.
  However,  the adjtime() function is not specified by POSIX.  Therefore, the
  existing BSD interface is preserved.




RETURN VALUES
  Upon successful completion, the adjtime() function returns a 0 (zero).  If
  the adjtime() function fails, a value of -1 is returned, and errno is set
  to indicate the error.

ERRORS
  If the adjtime() function fails, errno may be set to one of the following
  values:

  [EFAULT]  An argument address referenced invalid memory.

  [EPERM]   The process's effective user ID does not have appropriate system
	    privilege.

RELATED INFORMATION
  Functions: gettimeofday(2), gettimer(3)