unixdev.net


Switch to SpeakEasy.net DSL

The Modular Manual Browser

Home Page
Manual: (OSF1-V5.1-alpha)
Page:
Section:
Apropos / Subsearch:
optional field



adjtime(2)							   adjtime(2)



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

SYNOPSIS

  #include <&lt;sys/time.h>&gt;
  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 per-
  cent.	 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 com-
  puters 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.	 How-
  ever,	 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)