Optparse

optparse.hs

import qualified Options.Applicative as OA

data AppArgs =
  AppArgs
    { inFilePath :: !String
    , outFilePath :: !String
    , sampleFilter :: !Int
    }
  deriving (Show)

main :: IO ()
main = OA.execParser opts >>= runWithOptions
  where
    parser =
      AppArgs <$> OA.argument OA.str (OA.metavar "inCSV") <*>
      OA.argument OA.str (OA.metavar "outCSV") <*>
      OA.option OA.auto (OA.metavar "sample_filter" <> OA.value 0)
    opts = OA.info parser mempty