Haskell lazy I/O and closing files 3

import Control.Monad
import Data.Digest.MD5 (hash)
import Data.Word
import List (sort)
import Prelude
import System.Directory
import System.FilePath
import Text.Printf (printf)
import qualified Data.ByteString as BS

main :: IO ()

main = putStr . unlines =<< getList "."

getList :: FilePath -> IO [String]

getList p = mapM getFileLine =<< getRecursiveContents p
    where
        getFileLine path = liftM
                (\c -> (hex (hash (BS.unpack c))) ++ " " ++ path)
                (BS.readFile path)

hex :: [Word8] -> String

hex = concatMap (\x -> printf "%0.2x" (toInteger x))

getRecursiveContents :: FilePath -> IO [FilePath]

getRecursiveContents topdir = do
        names <- getDirectoryContents topdir

        let properNames = filter (`notElem` [".", ".."]) names

        paths <- concatForM properNames $ \name -> do
                let path = topdir </> name

                isDirectory <- doesDirectoryExist path
                if isDirectory
                        then getRecursiveContents path
                        else do
                                isFile <- doesFileExist path
                                if isFile
                                        then return [path]
                                        else return []

        return (sort paths)

concatForM :: (Monad m) => [a1] -> (a1 -> m [a]) -> m [a]

concatForM xs f = liftM concat (forM xs f)