import Control.Exception
import System.Environment
import System.IO

main = handle ioExpHandler $ do
    [from, to] <- getArgs
    withFile from ReadMode $ \hFrom ->
        withFile to WriteMode $ \hTo ->
            until (hIsEOF hFrom) $ do
                line <- hGetLine hFrom
                hPutStrLn hTo line
  where
    ioExpHandler :: IOException -> IO ()
    ioExpHandler e = putStrLn $ "fatal: " ++ show e
    until :: IO Bool -> IO a -> IO ()
    until bool act = bool >>= \x -> case x of
                        False -> act >> until bool act
                        True  -> return ()