adjtime(2)							    adjtime(2)

NAME    [Toc]    [Back]

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

SYNOPSIS    [Toc]    [Back]

     #include <sys/time.h>

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

DESCRIPTION    [Toc]    [Back]

     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, 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 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 a process with the super-user	privilege can adjust the time of day.

     The adjustment value will be silently rounded to the resolution of	the
     system clock.

RETURN    [Toc]    [Back]

     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    [Toc]    [Back]

     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 process'	allocated address space	that
			 is not	writable.

     EPERM		 The calling process does not have the super-user
			 privilege to change the time of day.




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adjtime(2)							    adjtime(2)



     EINVAL		 The value of delta is not an acceptable value,	it is
			 either	too large or too small.

SEE ALSO    [Toc]    [Back]

     date(1), gettimeofday(3C)


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