Streamline the process of working through the Getting Started with Grunt book and constantly creating a new directory with a new Gruntfile in the directory for each exercise.

Gruntfile.js

// purpose: Streamline the process of working through the Getting Started with Grunt book and constantly creating a
//          new directory with a new Gruntfile in the directory for each exercise.
//
// use:     First create a directory for working through the exercises. Next, get your dependencies all taken care of in
//          this directory by using '$ npm init' to create a package.json file. Now, get grunt in this directory using
//          '$ npm install --save-dev grunt'. Although you will need more dependencies through the course of the book,
//          this is enough to get started. Now, getting started on a new exercise is as simple as using
//          '$ grunt newEx:<chapter number>:<exercise number>'. For instance, if starting on chapter three, exercise
//          four, just enter '$ grunt newEx:03:04'. This grunt will create ./04/0403/Gruntfile.js. Now start editing
//          the Gruntfile to do the exercise.

// import modules
path = require('path');
fs = require('fs');

module.exports = function(grunt){

    // create new exercise task with two parameters, the chapter number and the exercise number
    grunt.registerTask('newEx', function(){

        // make sure the process does not exit early
        var done = this.async();

        // give access within the function to variables
        var params = this.args;

        // create full path to where the new exercise will reside
        var exGrunt = path.join(__dirname, params[0], params[0] + params[1], 'Gruntfile.js');

        // see if the exercise already exists
        fs.exists(exGrunt, function(exists){

            // if it exists, warn the user and exit
            if (exists) {
                grunt.fail.warn('Chapter ' + params[0] + ', exercise ' + params[1] + ' already exists.');

            // if it does not exist, create
            } else {

                // create and place a new Gruntfile in the directory
                var comment = '// chapter ' + params[0] + ' exercise ' + params[1];
                grunt.file.write(exGrunt, comment);

                // let grunt know it is done
                done();
            }
        });
    });
};