Unix tail using pipes library

Unix.hs

module Unix where

import Data.Foldable (traverse_)
import System.IO

import           Control.Monad.Trans
import           Pipes
import           Pipes.Parse
import qualified Pipes.Prelude as P

produceFile :: FilePath -> Producer' String IO ()
produceFile path = do
    h <- liftIO $ openFile path ReadMode
    P.fromHandle h

tailParser :: Parser String IO ()
tailParser = go [] (0 :: Int) where
  go xs len = do
      iopt <- draw
      case iopt of
          Nothing -> liftIO $ traverse_ print $ reverse xs
          Just l
              | len == 10 -> go (l:init xs) len
              | otherwise -> go (l:xs) (len+1)

unixTail :: FilePath -> IO ()
unixTail path = evalStateT tailParser (produceFile path)