readFile.hs

processDevice :: FilePath -> IO Int
processDevice fp = do
  contents <- readFile $ fp ++ "/size"
  return $ read contents

main = do
  files <- getDirectoryContents "/sys/block/sda"
  print $ map processDevice files

-- blockdevice.hs:33:2:
--     No instance for (Show (IO Int))
--       arising from a use of `print' at blockdevice.hs:33:2-6
--     Possible fix: add an instance declaration for (Show (IO Int))
--     In the first argument of `($)', namely `print'
--     In the expression: print $ map processDevice files
--     In the expression:
--         do { files <- getDirectoryContents "/sys/block/sda";
--                print $ map processDevice files }
-- Failed, modules loaded: none.