command line parser for various language

argparse.scala

object ParseArg {

  val usage = "Usage: argparse --s1 v1 --s2 v2 --f opt"

  def main(args: Array[String]) = {

    if (args.length == 0) {System.err.println(usage); System.exit(1)}

    def parseArg(argparsed: Map[Symbol,Any], arglist: List[String]): Option[Map[Symbol,Any]] = {
      arglist match {
        case Nil => Some(argparsed)
        case ("--switch1" | "-s1") :: v1 :: tail => parseArg(argparsed ++ Map('s1 -> v1), tail)
        case ("--switch2" | "-s2") :: v2 :: tail => parseArg(argparsed ++ Map('s2 -> v2), tail)
        case ("--flag" | "-f") :: tail => parseArg(argparsed ++ Map('f -> true), tail)
        case others :: tail if others(0) == '-' => println("Unknown switch: " + others); None
        case opt :: tail => parseArg(argparsed ++ Map('opt -> opt), arglist.tail)
      }
    }

    val pargs = parseArg(Map('f -> false), args.toList)
    if (pargs.isDefined) pargs.get.foreach(println)

  }

}

argparse_.py

#!/usr/bin/env python

import argparse

def getArgParser():
    parser = argparse.ArgumentParser(
             description="this is the usage string",
             formatter_class=argparse.ArgumentDefaultsHelpFormatter)
    parser.add_argument("opt1", metavar='opt1', type=str, 
                        help="the positional argument.")
    parser.add_argument("opt2", metavar='opt2', type=str, nargs='?', default="foo",
                        help="positional argument with a default.")
    parser.add_argument("-a", "--auto", action="store_true", 
                        help="the flag argument")
    parser.add_argument("-n", "--nitem", metavar='N', type=int, action="store", default=10,
                        help="switch of integer argument")
    return parser

def main():
    parser = getArgParser()
    args = parser.parse_args()
    for k, v in args.__dict__.items():
        print k, v

if __name__ == "__main__":
    main()

• argparse.scala
  • purely pattern matching solution
  • positional argument only allowed once (the last one)
• argparse_.py
  • depend on argparse