The 50-year-old Unix legend that’s quietly powering the most advanced AI agents today.
Born in the golden age of Unix at Bell Labs
While working on the Unix operating system, Ken Thompson extracted the regular expression engine from the ed editor
(g/re/p = global / regular expression / print). It started as a private tool called “s” (search) that he improved overnight for his colleague Doug McIlroy.
Grep became a fundamental Unix tool. Variants like egrep and fgrep emerged. It spread to every operating system and became essential for sysadmins, developers, and data analysts worldwide.
Andrew Gallant (BurntSushi) releases ripgrep — a blazing-fast Rust rewrite. It uses memory mapping, parallel processing, and smart filtering. Today it powers VS Code’s “Find in Files” and most modern AI coding agents.
In 2025–2026, something remarkable happened. The most advanced AI coding agents started using good old grep (and ripgrep) as their primary retrieval mechanism.
“When you give an AI agent the same tools a senior developer uses — grep, read file, shell — it often performs better than when you give it fancy vector search.”
Real tools and breakthroughs using grep today
Claude Code agents use ripgrep/ugrep as their core search engine when exploring large codebases. No heavy RAG — just pure, fast grep + file reading in an agent loop.
Cursor’s AI composer and agent features rely heavily on ripgrep for codebase context. Combined with massive context windows, it delivers extremely accurate code understanding.
Rigorous study showed that lexical grep retrieval frequently beats vector-based semantic search when used inside capable agent harnesses — especially for code tasks.
Read the paper →Structural search tool that understands code syntax (not just text). AI agents are now being taught to write sophisticated ast-grep rules for precise refactoring and analysis.
New tools like mgrep and AI-grep combine the speed and CLI feel of traditional grep with embeddings for natural language queries across code, PDFs, and more.
Popular open-source AI pair programmers and CLI agents all expose grep/ripgrep tools to the model. The pattern is clear: give the AI powerful, familiar tools and it thrives.
Experience classic grep + an AI twist right here
This demo uses JavaScript to simulate real grep behavior with regex highlighting.
The future of AI agents isn’t replacing classic tools — it’s mastering them.