int adjtime(const struct timeval *delta, struct timeval *olddelta);
This function speeds up or slows down the system clock in order to
make a gradual adjustment. This ensures that the calendar time
reported by the system clock is always monotonically increasing, which
might not happen if you simply set the clock.
argument specifies a relative adjustment to be made to the clock time.
If negative, the system clock is slowed down fora while until it has
lost this much elapsed time. If positive, the system clock is speeded
up for a while.
argument is not a null pointer, the
function returns information about any previous time adjustment that
has not yet completed.
This function is typically used to synchronize the clocks of computers
in a local network. You must be a privileged user to use it.
function returns 0 on success and -1 on failure and sets the external
The calling process does not have enough privileges to access the clock.
With a Linux kernel, you can use the
function to permanently change the system clock speed.