Skip site navigation (1)Skip section navigation (2)

FreeBSD Man Pages

Man Page or Keyword Search:
Man Architecture
Apropos Keyword Search (all sections) Output format
home | help
ADJTIME(2)		  FreeBSD System Calls Manual		    ADJTIME(2)

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

LIBRARY
     Standard C	Library	(libc, -lc)

SYNOPSIS
     #include <sys/time.h>

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

DESCRIPTION
     The adjtime() system call makes small adjustments to the system time, as
     returned by gettimeofday(2), advancing or retarding it by the time	speci-
     fied by the timeval delta.	 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.
     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 not a null	pointer, the
     structure pointed to will contain,	upon return, the number	of microsec-
     onds still	to be corrected	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() system call is restricted to	the super-user.

RETURN VALUES
     The adjtime() function returns the	value 0	if successful; otherwise the
     value -1 is returned and the global variable errno	is set to indicate the
     error.

ERRORS
     The adjtime() system call will fail if:

     [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)

     R.	Gusella	and S. Zatti, TSP: The Time Synchronization Protocol for UNIX
     4.3BSD.

HISTORY
     The adjtime() system call appeared	in 4.3BSD.

FreeBSD	9.2			 June 4, 1993			   FreeBSD 9.2

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | HISTORY

Want to link to this manual page? Use this URL:
<http://www.freebsd.org/cgi/man.cgi?query=adjtime&sektion=2&manpath=FreeBSD+9.2-RELEASE>

home | help