--- title: "Regular expressions that work “everywhere”" url: https://daily.dev/posts/regular-expressions-that-work-everywhere--eazvtdam6 source_url: https://www.johndcook.com/blog/2026/06/23/regex-everywhere type: article source: "Lobsters" published: 2026-06-29T16:06:44.098Z updated: 2026-06-29T16:07:01.910Z tags: ["linux", "bash"] reading_time: 3 upvotes: 0 comments: 0 language: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Regular expressions that work “everywhere” **[Lobsters](https://daily.dev/sources/lobsters)** · 3 min read · 0 upvotes · 0 comments ## Summary A practical guide to identifying which regular expression features work across multiple tools — specifically sed, awk, grep, and Emacs. The strictest portable subset includes only literals, character classes, and basic special characters. Using GNU versions with the -E flag expands compatibility, with awk serving as the lowest common denominator. Emacs is the main oddball, requiring backslashes before metacharacters like +, ?, (, ), {, }, and | and using different whitespace class syntax. A consolidated list of features that work across all four tools is provided, including dot, anchors, character classes, quantifiers, alternation, capturing groups, backreferences, and word boundary markers — with a caveat about gawk's backreference support. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Similar posts on daily.dev - [The true power of regular expressions](https://daily.dev/posts/the-true-power-of-regular-expressions-bmqlp7bsa) · Hacker News · 0 upvotes · 0 comments --- Tags: [#linux](https://daily.dev/tags/linux), [#bash](https://daily.dev/tags/bash) [View this post on daily.dev](https://daily.dev/posts/regular-expressions-that-work-everywhere--eazvtdam6)