[Haskell-cafe] How to generalize executing a series of commands, based on a list?

17 Nov 2010

      I am able to use System.Cmd (system) to invoke a shell command
and interpret the results.

Please see the code below that works okay for one such command.
(I invoke a program, passing two args.)

I am wondering how to generalize this to do likewise for a
series of commands, where the varying args (filenames, in this
case) are in a list ('inOutLeafs').

I will also want to accumulate some results; probably just a
failure count at this time.

Any advice or pointers to examples would be much appreciated.

Thanks in advance,
-- Peter
...
run :: ... -> IO (Int)    -- will return a fail count
run
   -- some args to this function here...
   = do
      -- ... set up: inputLeafs, outputLeafs, etc.
-- zip two lists of filenames:
      let inOutLeafs = zip inputLeafs outputLeafs
-- the first pair for the first command:
      let (inFile1,outFile1) = head inOutLeafs
-- build 1st command using 1st pair of filenames:
      let cmd1 = ...
exitCode <- system cmd1
      case (exitCode) of
         ExitSuccess -> do
            putStrLn $ "-- OK."
            return 0
         ExitFailure failCnt -> do
            putStrLn $ "-- Failed: " ++ show failCnt
            return 1

[Haskell-cafe] How to generalize executing a series of commands, based on a list?

Peter Schmitz