Count words in file in Haskell

words.hs

import Control.Exception
import System.Environment (getArgs)

catchAny :: IO a -> (SomeException -> IO a) -> IO a
catchAny = Control.Exception.catch

parseArgs :: [a] -> a
parseArgs args
    | (length args) == 1 = head args
    | otherwise = error "Invalid args. \nUsage: words <file>"

countWords :: String -> Int
countWords inp = sum $ map (length . words) (lines inp)

main :: IO ()
main = do
    args <- getArgs
    let fileName = parseArgs args
    input <- catchAny (readFile fileName) $ \e -> do
        error "Could not read file specified"
    print $ countWords input