The original poster wants to - read a file - get the contents as a String - break the string into lines - do something with the lines - and presumably print the result Easy. Put the following lines in a file called 'rf.hs': file_name = "rf.hs" main = readFile file_name >>= \string -> putStr (process (lines string)) process lines = maximum lines ++ "\n" Then m% ghc rf.hs m% ./rf => process lines = maximum lines ++ "\n" Explanation: readFile file_name is an IO action which when performed will read the named file and deliver a string cmd1 >>= \x -> cmd2 is an IO action which when performed will first perform cmd1, then bind its result to x, and then perform cmd2. >>= is the fundamental operation for chaining actions together. lines is a plain old String -> [String] function process is a plain old [String] -> String function, whatever you want putStr x is an IO action which when performed will write x The run time environment causes main to be performed.