Regular expressions that work “everywhere”

This article discusses the challenge of varying regular expression implementations across different tools and provides a practical guide to using a subset of regex features that work consistently in sed, awk, grep, and Emacs. It explains how awk serves as a lowest common denominator, notes Emacs as an oddball with different syntax requirements, and lists compatible features such as literals, character classes, anchors, quantifiers, alternation, capturing groups, and backreferences. The author emphasizes avoiding advanced features like look-around to ensure portability, making it useful for developers who need cross-platform regex solutions.