A simple command line utility template for Groovy. Functionality can be implemented by declaring new methods of the form "_doXYZ" where XYZ is the name of the command to run.

GroovyCLI.groovy

/**
 * Base class for command line applications.
 *
 * Children can provide functionality in the form of
 *      <command name> <arguments...>
 *
 * @author Ben Fagin
 */
class GroovyCLI implements Runnable {
  private String[] args;

	// invoked at the command line
	GroovyCLI(String[] args) {
		this.args = args
	}

	void run() {
		// argument parsing
		def newArgs

		if (args.length < 1) {
			throw new RuntimeException("usage <command name :: 1> <args :: 0+>")
		} else if (args.length == 1) {
			newArgs = {}
		} else {
			newArgs = args[1..args.length-1]
		}

		// make the command name
		def cmd = args[0].toLowerCase()
		if (cmd.length() > 0) {
			def firstChar = Character.toUpperCase(cmd.charAt(0))
			firstChar = Character.toString(firstChar)
			cmd = firstChar + cmd.substring(1)
		}

		// run the command
		try {
			"_do${cmd}"(newArgs)
		} catch (MissingMethodException ex) {
			throw new RuntimeException("Command '${cmd}' not recognized.")
		}
	}
}

MyApp.groovy

import groovy.transform.InheritConstructors

/**
 * Example application. Pass this as the main class, and Groovy will
 * construct the object with the arguments, and then invoke the
 * specified command as per the run() method in {@link GroovyCLI}.
 *
 * @author Ben Fagin
 */
@InheritConstructors
class MyApp extends GroovyCLI {

	// a single command called 'test'
	// expects any number of arguments

	void _doTest(def args) {
		println("${args.size()} arguments")
		println(args)
	}
}