Suppose you have a system that keeps track of thousands of users' contact information, including email address. This information is stored in plain text, on disk in a hierarchical directory structure (on a Unix operating system) organized by year, month, and day it was entered in the system. Something bad happens and the system crashes. We want to get the email address of all these users to notify them. How would you parse these directories and files to generate a simple list of email addresses?
