Question

I’m fairly new to Scala and need to build a really simple command line parser which provides something like the following which I created using JRuby in a few minutes:-

java -jar demo.jar --help

Command Line Example Application

Example: java -jar demo.jar --dn "CN=Test" --nde-url "http://www.example.com" --password "password"

For usage see below:

    -n http://www.example.com
    -p, --password             set the password
    -c, --capi                 set add to Windows key-store
    -h, --help                 Show this message
    -v, --version              Print version

Scallop looks like it will do the trick, but I can’t seem to find a simple example that works! All of the examples I’ve found seem to be fragmented and don’t work for some reason or other.

UPDATE

I found this example which works, but I’m not sure how to bind it into the actual args within the main method.

import org.rogach.scallop._; 

object cmdlinetest {
  def main(args: Array[String]) 

    val opts = Scallop(List("-d","--num-limbs","1"))
      .version("test 1.2.3 (c) 2012 Mr Placeholder")
      .banner("""Usage: test [OPTION]... [pet-name]
                |test is an awesome program, which does something funny
                |Options:
                |""".stripMargin)
      .footer("\nFor all other tricks, consult the documentation!")
      .opt[Boolean]("donkey", descr = "use donkey mode")
      .opt("monkeys", default = Some(2), short = 'm')
      .opt[Int]("num-limbs", 'k',
      "number of libms", required = true)
      .opt[List[Double]]("params")
      .opt[String]("debug", hidden = true)
      .props[String]('D',"some key-value pairs")
      // you can add parameters a bit later
      .args(List("-Dalpha=1","-D","betta=2","gamma=3", "Pigeon"))
      .trailArg[String]("pet name")
      .verify

    println(opts.help)
  }
}

Answer 1

Well, I’ll try to add more examples 🙂

In this case, it would be much better to use ScallopConf:

import org.rogach.scallop._

object Main extends App {
  val opts = new ScallopConf(args) {
    banner("""
NDE/SCEP Certificate enrollment prototype

Example: java -jar demo.jar --dn CN=Test --nde-url http://www.example.com --password password

For usage see below:
    """)

    val ndeUrl = opt[String]("nde-url")
    val password = opt[String]("password", descr = "set the password")
    val capi = toggle("capi", prefix = "no-", descrYes = "enable adding to Windows key-store", descrNo = "disable adding to Windows key-store")
    val version = opt[Boolean]("version", noshort = true, descr = "Print version")
    val help = opt[Boolean]("help", noshort = true, descr = "Show this message")

  }

  println(opts.password())
}

It prints:

$ java -jar demo.jar --help

NDE/SCEP Certificate enrollment prototype

Example: java -jar demo.jar --dn CN=Test --nde-url http://www.example.com --password password

For usage see below:

  -c, --capi              enable adding to Windows key-store 
      --no-capi           disable adding to Windows key-store 
      --help              Show this message 
  -n, --nde-url  <arg>     
  -p, --password  <arg>   set the password 
      --version           Print version