get32rand.hs

module Main where

import Data.Char
import Data.ByteString.Char8 hiding (all, putStrLn)
import System.IO

getStr _ 0 _ = return ""
getStr h n p = do
    c <- unpack <$> hGet h 1
    if all p c
      then do
          s <- getStr h (n - 1) p
          return $ c ++ s
      else getStr h n p
get32 h = hSetBuffering h NoBuffering >> getStr h 32 (and . ([isAlphaNum, isAscii] <*>) . pure)
get32Rand = withFile "/dev/urandom" ReadMode get32 >>= putStrLn

main :: IO ()
main = get32Rand