Course
Regex & Text Processing
Regular expressions as a professional tool — how backtracking engines really execute your patterns, captures and lookarounds done right, the performance traps behind real outages, and when grep, sed, awk, or jq (or a real parser) beats a clever regex.
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Engines and Mental Models
How engines execute patterns, how quantifiers and anchors really behave, and why the same regex means different things in different tools.
- 01How Regex Engines Actually MatchBacktracking versus automata engines, what a choice point costs, and the mental model that lets you predict a pattern's behavior before you run it.22mOpen
- 02Quantifiers, Classes, and Anchors: Saying Exactly What You MeanGreedy, lazy, and possessive quantifiers, why negated classes beat lazy dots, and the anchors that turn 'contains' into 'is'.20mOpen
- 03Dialects: BRE, ERE, PCRE, JavaScript, and RE2Why a pattern that works in regex101 silently matches nothing in sed — flavor differences, escaping layers, and leftmost-longest versus leftmost-first.20mOpen
Precision Matching
Capture groups, backreferences, lookarounds, flags, and Unicode — extracting exactly what you meant and nothing else.
- 01Capture Groups, Backreferences, and ReplacementNumbered and named groups, non-capturing groups, the last-iteration trap, and the replacement syntax that differs in every tool.22mOpen
- 02Lookarounds: Matching on Context Without Consuming ItLookahead and lookbehind as zero-width assertions, engine support differences, and when a lookaround is cleverness you should replace with code.20mOpen
- 03Flags, Lines, and Unicode: Where Correct Patterns Go WrongMultiline and dotall semantics, the trailing-newline validation bypass, CRLF, code units versus code points, and the stateful g flag.22mOpen
Production Text Processing
Catastrophic backtracking, the Unix text toolkit, and the judgment call of when to stop using regex at all.
- 01Catastrophic Backtracking and ReDoSThe pattern shapes that turn a regex into a denial-of-service, the real outages they caused, and the fixes in order of preference.25mOpen
- 02The Unix Text Toolkit: grep, sed, awk, and jqEach tool's lane, the flags you'll actually use, and the incident-response pipelines that answer questions in seconds instead of scripts.28mOpen
- 03Knowing When Not to Use RegexThe formats regex can't parse, the security bugs that come from trying, and a decision checklist for regex versus parser versus pipeline.20mOpen