adjtime(2) [netbsd man page]

ADJTIME(2)						      BSD 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

     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 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.  If olddelta is non-nil, 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.

     If the calling user is not the super user, then the adjtime() function in the standard C library will try to use the clockctl(4) device if
     present, thus making possible for non privileged users to adjust the system time.	If clockctl(4) is not present or not accessible, then
     adjtime() reverts to the adjtime() system call, which is restricted to the super user.

RETURN VALUES

     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

     adjtime() 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), clockctl(4), timed(8), timedc(8)

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

HISTORY

     The adjtime() function call appeared in 4.3BSD.

BSD
								   June 4, 1993 							       BSD

adjtime(2)							System Calls Manual							adjtime(2)

NAME

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

SYNOPSIS

       #include <sys/time.h>
       int adjtime (	  struct timeval *delta,      struct timeval *old_delta );

PARAMETERS

       Points to the amount of time to be altered.  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 percent.	Thus, the time is always a monotonically increasing  func-
       tion.

       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()  func-
       tion 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 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() 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.  However,  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: An  argument  address	referenced  invalid  memory.   The
       process's effective user ID does not have appropriate system privilege.

RELATED INFORMATION

       Functions: gettimeofday(2), gettimer(3) delim off

																	adjtime(2)