The Well-Grounded Rubyist, Second Edition

6.4. Error handling and exceptions

Way back in chapter 1, we looked at how to test code for syntax errors:

$ ruby -cw filename.rb

Passing the -cw test means Ruby can run your program. But it doesn’t mean nothing will go wrong while your program is running. You can write a syntactically correct program—a program that the interpreter will accept and execute—that does all sorts of unacceptable things. Ruby handles unacceptable behavior at runtime by raising an exception.

6.4.1. Raising and rescuing exceptions

An exception is a special kind of object, an instance of the class Exception or a descendant of that class. Raising an exception means stopping normal execution of the program and either dealing with the problem that’s been encountered or exiting ...