CLI tool that auto-detects project commands to skip READMEs forever

Developers waste valuable time deciphering cryptic README files to determine the correct commands for running tests, starting servers, or installing dependencies. The process is repetitive, error-prone, and mentally draining. What if a single command could bypass all that friction?

That’s the promise of Rex, a command-line tool that automatically detects a project’s technology stack and executes the correct commands—no manual reading required.

Eliminating the README guessing game

Traditional workflows force developers into a tedious cycle:

• Clone a repository
• Scan the README for setup instructions
• Identify the correct package manager and command syntax
• Execute the command (often incorrectly)
• Repeat for every project

Rex removes this overhead by analyzing project files to determine the technology stack and running the appropriate commands. For example:

# Instead of:
git clone 
cd repo
pnpm test

# Use Rex:
git clone 
cd repo
rex test

The tool supports 12 ecosystems, from Go and Rust to Node.js, Python, and Ruby on Rails. It even detects package managers by examining lockfiles, ensuring the correct command is executed every time.

How Rex detects and executes commands

Rex scans the project root for key files to identify the stack and associated commands:

• go.mod → Go projects → go test ./...
• package.json + pnpm-lock.yaml → Node.js with pnpm → pnpm test
• Cargo.toml → Rust → cargo test
• pyproject.toml + uv.lock → Python with uv → uv run pytest
• composer.json + artisan → PHP Laravel → php artisan test
• Gemfile + app/ → Ruby on 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

The tool also supports monorepos, automatically detecting sub-projects and their respective stacks. This makes it ideal for large codebases with multiple services or libraries.

A transparent, no-surprises workflow

Rex prioritizes clarity by displaying the exact command it will execute before running it. For example:

$ cd my-go-project/
$ rex test
> go test ./...
ok  	github.com/example/app	1.2s

The > symbol indicates the command Rex will run, ensuring full transparency. This eliminates guesswork and prevents unexpected behavior in unfamiliar repositories.

Simplifying team workflows with rex.toml

To standardize commands across a team, developers can generate a rex.toml file using:

rex init

This file documents the project’s commands, which can then be committed to version control. Every team member can execute the same commands without manual configuration or documentation lookup.

From clone to execution in one step

One of Rex’s standout features is `rex clone`, which combines cloning a repository, detecting the stack, and installing dependencies into a single command:

rex clone 
# Output:
# cloning...
# detected: node + pnpm
# deps: pnpm install
# ready!

This reduces onboarding time for new developers and ensures consistency across projects. The tool also automatically loads .env files, further streamlining the setup process.

Built for speed and reliability

Rex is engineered for performance and minimal overhead:

• A single binary with no runtime dependencies
• Cross-platform support for Linux, macOS, and Windows
• Sub-50ms startup time, faster than most shell prompts
• Zero network calls, fully functional offline
• Correct exit codes for seamless integration with CI/CD pipelines
• Shell completions for bash, zsh, and fish

The tool is written in Go and distributed under the Apache 2.0 license, making it open-source and free to use. It has also been featured in the Awesome Go collection, a curated list of Go-based tools.

Getting started with Rex

Installing Rex is straightforward:

• Homebrew (macOS/Linux):

brew tap rexrun-dev/tap && brew install rex

• Go (cross-platform):

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

Pre-built binaries are also available for download from the project’s GitHub releases page.

The future of streamlined development

Rex addresses a persistent pain point in software development: the cognitive load of remembering project-specific commands. By abstracting away stack-specific syntax, it allows developers to focus on writing code rather than deciphering documentation. Whether you’re jumping between projects or onboarding new team members, Rex promises a smoother, faster, and more consistent experience.

The open-source nature of the project invites contributions from the community, whether through new stack support, bug fixes, or feature requests. For developers tired of the README guessing game, Rex offers a compelling solution—one command at a time.