I built a CLI that eliminates README reading forever

Question

---

title: I built a CLI that eliminates README reading forever
published: true
description: rex detects your project stack and runs the right command. Zero config. One binary. 12 ecosystems.
tags: go, cli, productivity, opensource

cover_image: https://rexrun.dev/logo.png

The problem

Every developer knows this pain:

1. Clone a repo
2. Want to run the tests
3. Open the README
4. Scroll... scroll... find a "Development" section... maybe
5. Figure out it's pnpm test (not npm test, not yarn test)
6. Run it wrong anyway because you needed pnpm install first

Multiply this by every repo you touch. Every PR you review. Every onboarding.

I got tired of it.

The solution: rex

git clone https://github.com/some/repo
cd repo
rex test

That's it. Rex looks at your project files, detects the stack, and runs the correct command. No config. No setup. No reading anything.

How it works

Rex reads files in your project root:

File found	Stack detected	rex test runs
go.mod	Go	go test ./...
package.json + pnpm-lock.yaml	Node + pnpm	pnpm test
Cargo.toml	Rust	cargo test
pyproject.toml + uv.lock	Python + uv	uv run pytest
composer.json + artisan	PHP + Laravel	php artisan test
Gemfile + app/	Ruby + Rails	bundle exec rails test
pom.xml	Java + Maven	mvn test
build.gradle	Java + Gradle	./gradlew test
build.zig	Zig	zig build test
mix.exs	Elixir	mix test
Makefile	Make	make test
Justfile	Just	just test

12 ecosystems. It also detects which package manager you use by looking at lockfiles.

Demo

Watch the video demo

$ cd my-go-project/
$ rex

  my-go-project

  stack  go

  commands
    rex test   go test ./...
    rex run    go run ./cmd/server
    rex build  go build ./...
    rex deps   go mod download
    rex fmt    gofmt -w .
    rex lint   go vet ./...

$ rex test
> go test ./...
ok   github.com/example/app   1.2s

The > arrow always shows exactly what rex will run. Full transparency.

All the verbs

Command	What it does
rex test	Run tests
rex run	Start the app / dev server
rex build	Build the project
rex deps	Install dependencies
rex clean	Remove build artifacts
rex fresh	clean, deps, build in sequence
rex fmt	Format code
rex lint	Lint code
rex clone <url>	Clone + detect + install deps in one command
rex init	Generate rex.toml for your team
rex doctor	Diagnose environment issues

Killer feature: rex clone

rex clone https://github.com/someone/project
# cloning...
# detected: node + pnpm
# deps: pnpm install
# ready! cd project && rex run

From URL to working project in one command. No README needed.

Monorepo support

Rex auto-detects monorepos (packages/, apps/, services/):

$ rex

  my-monorepo (monorepo)

  workspace  3 sub-projects detected

    packages/api         node + pnpm
    packages/web         node + pnpm
    services/auth        go

Team workflow: rex init

rex init
# created rex.toml (go project)

Generates a rex.toml from detected commands. Commit it. Now every teammate runs the same commands without asking.

.env loading

Rex automatically loads .env files before running commands. No extra tools needed.

Why I built this

I maintain projects across Go, Node, Python, and Rust. I context-switch between repos dozens of times per day. The cognitive load of remembering pnpm test vs go test ./... vs cargo test is small individually, but it adds up.

Rex makes every repo feel the same:

rex test   # always works
rex run    # always works
rex build  # always works

It's the muscle memory tax I no longer pay.

Technical details

• Single binary, no runtime, no dependencies
• Written in Go, cross-platform
• Less than 50ms startup, faster than your shell prompt
• Zero network calls, fully offline
• Correct exit codes, works in CI
• Shell completions for bash, zsh, fish
• Apache 2.0 license
• Mentioned in Awesome Go

Install

# Homebrew (macOS/Linux)
brew tap rexrun-dev/tap && brew install rex

# Go
go install rexrun.dev/rex/cmd/rex@latest

Or grab a binary from GitHub Releases.

Links

• GitHub: github.com/rexrun-dev/rex
• Website: rexrun.dev

If this solves a pain you've felt, star the repo. If you want a stack added, open an issue.