How to sleep for few milliseconds in swift 2.2?

please anyone tell me how to use sleep() for few milliseconds in swift 2.2?

while (true){
    print("sleep for 0.002 seconds.")
    sleep(0.002) // not working
}

but

while (true){
    print("sleep for 2 seconds.")
    sleep(2) // working
}

it is working.

UPDATE: For Swift 5.5 and later, you can use this

let seconds = UInt64(2)
print("paused at \(Date())")
Task {
    do {
        try await Task.sleep(nanoseconds: seconds * 1_000_000_000)
        print("started again at \(Date()) after \(seconds) seconds")
    } catch {
        print("An error occurred: \(error.localizedDescription)")
    }
}

----------------------------------------------------------------

usleep() takes millionths of a second

usleep(1000000) //will sleep for 1 second
usleep(2000) //will sleep for .002 seconds

OR

 let ms = 1000
 usleep(useconds_t(2 * ms)) //will sleep for 2 milliseconds (.002 seconds)

OR

let second: Double = 1000000
usleep(useconds_t(0.002 * second)) //will sleep for 2 milliseconds (.002 seconds)