Sleep function. May block for longer than requested, with the actual wait time determined by the capabilities of the underlying system.
integer number of milliseconds to block the caller.
If 'msec' is non-integer, it will be coerced to integer. Non-numeric input will be ignored and return immediately.
Note that unlike
Sys.sleep, this function is not
user-interruptible by sending SIGINT e.g. with ctrl + c.