Chapter 11. Regular expressions and regexp-based string operations

In this chapter, we’ll explore Ruby’s facilities for pattern matching and text processing, centering around the use of regular expressions. A regular expression in Ruby serves the same purposes it does in other languages: it specifies a pattern of characters, a pattern that may or may not correctly predict (that is, match) a given string. Pattern-match operations are used for conditional branching (match/no match), pinpointing substrings (parts of a string that match parts of the pattern), and various text-filtering techniques.

Regular expressions in Ruby are objects, specifically instances of the Regexp class. Like all other objects in Ruby, you send messages to a regular expression.

We’ll start with an overview of regular expressions. From there, we’ll move on to the details of how to write them and, of course, how to use them. In the latter category, we’ll look at using regular expressions both in simple match operations and in methods where they play a role in a larger process, such as filtering a collection or repeatedly scanning a string.

11.1. What are regular expressions?

11.2. Writing regular expressions

11.3. Building a pattern in a regular expression

11.4. Matching, substring captures, and MatchData

11.5. Fine-tuning regular expressions with quantifiers, anchors, and modifiers

11.6. Converting strings and regular expressions to each other

11.7. Common methods that use regular expressions

Summary