CSC/ECE 517 Summer 2008/wiki1 5 bk

Understanding Hooks

The hooking mechanism in Ruby allows certain functional events inside a running program to be identified while providing an action that will occur upon detection of the specified event. In this way, hooks serve as a detector of actions within the code. Examples of where such a technique would prove useful include:

• Recording when or how many times a method is called.
• Recording when an object is created.
• Debugging problematic code.

module Kernel

 alias_method :original_system, :system
 def system(*args)
   puts "Your program executed the \"#{args.join(', ')}\" command." 
   puts "It was executed at: " + `date`
   puts "The command output the following: "
   original_system(*args)
 end

end system("ls -al")