text_reader.hs

-- read a text file
-- print a line, wait for return by user, repeat. exits when no more lines to print

import System.Environment
import System.IO
import System.Exit

parse ["-h"] = putStrLn "./text_reader [-h] file" >> exitWith ExitSuccess
parse [f] = readFile f

waitAndPrint [] = putStrLn "-- end" >> exitWith ExitSuccess
waitAndPrint (x:xs) = do
    c <- getChar
    putStrLn x
    waitAndPrint xs

main = do
    args <- getArgs
    f <- parse args
    let contents = lines f
        firstLine = head contents
        rest = tail contents
    putStrLn firstLine
    waitAndPrint rest

-- $ ghc --make text_reader
-- $ ./text_reader -h
-- ./text_reader [-h] file
-- $ ./text_reader test.txt
-- i am a file
--
-- with a few
--
-- text lines!
-- -- end
-- $