Just

Just Command Runner

GitHub Repository

just is a handy way to save and run project-specific commands. It's a command runner, not a build system, avoiding much of make's complexity.

Instructions

Prerequisites

• just must be installed: brew install just
• Commands are stored in a justfile (or Justfile).

Common Settings (set ...)

You can configure just behavior at the top of your justfile:

• set shell := ["bash", "-c"]: Change the default shell.
• set dotenv-load: Automatically load .env files.
• set allow-duplicate-recipes: Allow overriding recipes.
• set fallback: Search for justfile in parent directories.
• set quiet: Don't echo commands by default.

Example Justfiles

For complete reference, see these templates:

• Node.js + Docker
• Python + Venv
• Bun + TypeScript
• Astral UV + Python
• Multi-Module / Advanced

Workflow

1. Create a justfile: Define recipes at the top level of your project. Always include a default recipe that lists available commands:

   justCopy code
   default:
     @just --list
   

   justCopy code
   # The default recipe (runs when calling `just` with no args)
   default:
     just --list
   
   # A basic recipe
   test:
     cargo test
   
   # A recipe with parameters
   build target:
     echo "Building {{target}}..."
     cc main.c -o {{target}}
   

2. Run Recipes:

   • Run the default recipe: just
   • Run a specific recipe: just <recipe>
   • Pass arguments to a recipe: just build my-app
   • List all available recipes: just --list

3. Advanced Features:

   • Dependencies: test: build (runs build before test).
   • Shebang Recipes: Use other languages like Python or Node inside a recipe.

     justCopy code
     python-task:
       #!/usr/bin/env python3
       print("Hello from Python!")
     

   • Dotenv: set dotenv-load at the top of the file to load .env.

Examples

Example 1: Standard Development Justfile

User request:

Copy code
Create a justfile for my Node project to handle lint, test, and dev

You would:

1. Create a justfile:

   justCopy code
   default:
     @just --list
   
   lint:
     npm run lint
   
   test:
     npm test
   
   dev:
     npm run dev
   

2. Tell the user they can now run just dev or just test.

Example 2: Recipe with Parameters

User request:

Copy code
Add a recipe to just to deploy to a specific environment

You would:

1. Edit the justfile:

   justCopy code
   deploy env:
     echo "Deploying to {{env}}..."
     ./scripts/deploy.sh --target {{env}}
   

2. Inform the user they can run just deploy production.

Example 3: Listing Recipes

User request:

Copy code
What commands are available in this project?

You would:

1. Run just --list to see available recipes and their comments.