Read until end of stream in haskell

This goes way beyond what you're really asking for, but I use this pattern a lot: interact:

myFun :: String -> String
myFun = ...

main = interact (unlines . myFun . lines)

Your function myFun will be executed against every line of standard input and the result sent to standard output.

Use isEOF from System.IO.

import System.IO (isEOF)
import Data.Char

main = myLoop

myLoop = do done <- isEOF
            if done
              then putStrLn "Bye!"
              else do inp <- getLine
                      putStrLn (map toUpper inp)
                      myLoop