Just — A Modern Command Runner and Makefile Alternative

What it is

Just is a command runner that serves as a modern replacement for Make. You write recipes in a Justfile with a simple syntax, and run them with just recipe-name. Unlike Make, Just has no file-dependency system -- it focuses purely on running commands with a clean, predictable syntax.

Just targets developers who use Makefiles as command shortcuts rather than build systems. It eliminates Make's quirks (tabs vs spaces, implicit rules, shell differences) and adds features like arguments, variables, and recipe dependencies.

How it saves time or tokens

Just reduces project onboarding time. New team members run just --list to see all available commands. Each recipe has a description and a clear invocation pattern. No more reading through a 200-line Makefile to find the deploy command.

For AI agents, Justfiles are easier to parse and generate than Makefiles because the syntax is simpler and more consistent.

How to use

1. Install Just:

brew install just         # macOS
cargo install just        # Rust
scoop install just        # Windows

1. Create a Justfile in your project root:

# Start development server
dev:
    npm run dev

# Run tests with optional filter
test filter='':
    go test ./... -run '{{filter}}'

# Deploy to production
deploy: test
    bash deploy.sh production

# Format and lint
check:
    go fmt ./...
    golangci-lint run

1. Run recipes:

just dev
just test MyFunction
just deploy
just --list

Example

# Justfile with variables, arguments, and conditionals
project := 'myapp'
env := env_var_or_default('ENV', 'development')

# Build the project
build target='all':
    @echo 'Building {{project}} ({{target}}) for {{env}}'
    go build -o bin/{{project}} ./cmd/{{target}}

# Run database migrations
migrate direction='up':
    goose -dir migrations {{direction}}

# Docker build and push
docker tag='latest':
    docker build -t {{project}}:{{tag}} .
    docker push registry.example.com/{{project}}:{{tag}}

# Clean build artifacts
clean:
    rm -rf bin/ dist/ tmp/

Related on TokRepo

• CLI and Automation Tools -- More command-line productivity tools
• AI Tools for DevOps -- Development operations and build tools

Common pitfalls

• Justfile recipes use sh by default on Unix. If you write bash-specific syntax (arrays, [[), set set shell := ['bash', '-cu'] at the top of your Justfile.
• Just does not track file dependencies like Make does. If you need incremental builds, use a build tool (Go, Cargo, webpack) inside your Just recipes.
• Recipe names cannot contain hyphens in some versions. Use underscores or camelCase for recipe names.