---
title: "grex Regular Expression Generator from Test Cases"
description: "grex is a command-line tool and library that automatically generates regular expressions from user-provided test cases. Written in Rust with Python bindings, it produces the most specific regex that matches the given input, supporting Unicode 16.0, character class detection, quantifier notation, and case-insensitive matching."
verification: "security_reviewed"
source: "https://github.com/pemistahl/grex"
category:
  - "Developer Tools"
framework:
  - "Custom Agents"
tool_ecosystem:
  github_repo: "pemistahl/grex"
  github_stars: 8079
---

# grex Regular Expression Generator from Test Cases

grex is a command-line tool and library that automatically generates regular expressions from user-provided test cases. Written in Rust with Python bindings, it produces the most specific regex that matches the given input, supporting Unicode 16.0, character class detection, quantifier notation, and case-insensitive matching.

## Installation

Choose whichever fits your setup:

1. Copy this skill folder into your local skills directory.
2. Clone the repo and symlink or copy the skill into your agent workspace.
3. Add the repo as a git submodule if you manage shared skills centrally.
4. Install it through your internal provisioning or packaging workflow.
5. Download the folder directly from GitHub and place it in your skills collection.

## Source

- [Agent Skill Exchange](https://agentskillexchange.com/skills/grex-regex-generator-from-test-cases/)