(Quick Reference)
                create-controller
Purpose
The 
create-controller command creates a controller and associated unit test for the given base name.
Examples
grails create-controller
grails create-controller Book
grails create-controller org.bookstore.book
Description
Creates a new controller with an empty default action. The argument is optional, but if you don't include it the command will ask you for the name of the controller.
A 
controller is responsible for handling incoming web requests and performing actions such as redirects, rendering views and so on.
The name of the controller can include a Java package, such as 
org.bookstore in the final example above, but if one is not provided a default is used. So the second example will create the file 
grails-app/controllers/<appname>/BookController.groovy whereas the last one will create 
grails-app/controllers/org/bookstore/BookController.groovy directory. Note that the first letter of the controller name is always upper-cased when determining the class name.
If you want the command to default to a different package for controllers, provide a value for 
grails.project.groupId in the 
runtime configuration.
Note that this command is just for convenience and you can also create controllers in your favourite text editor or IDE if you choose.
Usage:
grails create-controller [name]