Learn Regex the Easy Way, Part 6: Alternation and Grouping

Quick Recap # In Part 5, we covered metacharacters, escaping with backslash, and the dot wildcard. We learned the 14 special characters and how to match them literally. Now let’s combine patterns with “or” logic and control what our quantifiers apply to. The Pipe Means OR # The pipe character | means “or” in regex. cat|dog matches either “cat” or “dog.” Grouping with Parentheses # Here’s where it gets critical. Without parentheses, the pipe applies to everything on each side: cat|dog food # Matches "cat" OR "dog food" # NOT "cat food" or "dog food" With parentheses, you limit the scope: (cat|dog) # Either "cat" or "dog" [[:blank:]] # A space food # Literal "food" Compact: (cat|dog) food MATCH THESE cat food dog food DO NOT MATCH THESE bird food cat dog food Multiple Alternatives # You can have as many alternatives as you need: (red|green|blue|yellow). Grouping for Quantifiers # Parentheses also let you apply quantifiers to multi-character sequences: (ha)+ # One or more "ha" # Matches:…