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ADJTIME(2)		      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
       specified by the	timeval	delta.	If delta is  negative,	the  clock  is
       slowed  down  by	incrementing it	more slowly than normal	until the cor-
       rection 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 in-
       creasing	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 microseconds still to be corrected 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() 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)

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

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

FreeBSD	13.2			 May 13, 2021			    ADJTIME(2)

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

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