DragonFly On-Line Manual Pages

ADJTIME(2)               DragonFly 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 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 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
     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)

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

DragonFly 5.5-DEVELOPMENT        June 17, 2019       DragonFly 5.5-DEVELOPMENT