-- Not run on mingw, because of /dev/null use import System (system, ExitCode(..), exitWith) main = system "cat dog 1>/dev/null 2>&1" >>= \ ec -> case ec of ExitSuccess -> putStr "What?!?\n" >> ioError (userError "dog succeeded") ExitFailure _ -> system "cat system001.hs 2>/dev/null" >>= \ ec -> case ec of ExitSuccess -> exitWith ExitSuccess ExitFailure _ -> putStr "What?!?\n" >> ioError (userError "cat failed")