NAME    [Toc]    [Back]

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

SYNOPSIS    [Toc]    [Back]

     #include <sys/time.h>

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

DESCRIPTION    [Toc]    [Back]

     adjtime() 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 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  non-null,  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 call adjtime() is restricted to the superuser.

RETURN VALUES    [Toc]    [Back]

     A  return  value  of 0 indicates that the call succeeded.  A
return value of
     -1 indicates that an error occurred, and in this case an error code is
     stored in the global variable errno.

ERRORS    [Toc]    [Back]

     adjtime() will fail if:

     [EFAULT]      Either of the arguments point outside the process's allocated
 address space.

     [EPERM]       The process's effective user ID is not that of
the superuser.

SEE ALSO    [Toc]    [Back]

     date(1), gettimeofday(2), timed(8), timedc(8)

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

HISTORY    [Toc]    [Back]

     The adjtime() function call appeared in 4.3BSD.

OpenBSD      3.6                           June      4,      1993