just
Use `just` to save and run project-specific commands. Use when the user mentions `justfile`, `recipe`, or needs a simple alternative to `make` for task automation.
About this skill
This AI agent skill provides comprehensive knowledge about `just`, a modern command runner designed for defining and executing project-specific commands. It allows the agent to assist users in understanding, setting up, and utilizing `justfiles` (where commands, called 'recipes', are defined). The skill covers core functionalities such as creating a `default` recipe to list available commands, running specific recipes with or without parameters, and configuring `just` behavior through settings like shell selection or `.env` file loading. The agent can explain `just`'s advantages over `make` in terms of simplicity and readability, helping users streamline their development workflows. Key use cases include automating common development tasks like testing, building, or deploying, managing dependencies between tasks, and standardizing command execution across a project. By leveraging this skill, the AI agent can effectively introduce `just` to new users, provide guidance for its implementation, and troubleshoot common usage scenarios, making project task management more efficient and accessible.
Best use case
The primary use case is to help developers simplify and standardize their project's command execution and task automation. It's ideal for individual developers and teams who want a straightforward, human-readable way to define and run recurring development commands (e.g., `test`, `build`, `lint`) without the complexity associated with traditional build systems like `make`. This skill enables the AI agent to facilitate quick setup and effective use of `just`, improving workflow consistency and developer productivity.
Use `just` to save and run project-specific commands. Use when the user mentions `justfile`, `recipe`, or needs a simple alternative to `make` for task automation.
The user will successfully define, understand, and execute project-specific commands using `just` for streamlined task automation, guided by the AI agent.
Practical example
Example input
I want to set up a `justfile` for my Node.js project. How do I define `start` and `test` scripts, and how can I run them?
Example output
To set up a `justfile` for your Node.js project, first ensure `just` is installed (e.g., `brew install just`). Then, create a file named `justfile` in your project root with the following content: ```just default: @just --list start: node index.js test: npm test ``` To run the `start` script, type `just start` in your terminal. To run the `test` script, use `just test`. You can also just type `just` to see a list of available recipes.
When to use this skill
- When the user explicitly mentions `justfile`, `recipe`, or `just`.
- When the user needs a simple and readable alternative to `make` for project task automation.
- When the user wants to define and run project-specific commands consistently across environments.
- When assisting with setting up, configuring, or troubleshooting `just` in a development project.
When not to use this skill
- When a full-fledged, complex build system like `Bazel` or `Gradle` is explicitly required for sophisticated build graph management.
- When the project does not involve recurring commands or the need for task automation.
- When `make` or another command runner is already deeply integrated and meeting all project requirements effectively.
Installation
Claude Code / Cursor / Codex
Manual Installation
- Download SKILL.md from GitHub
- Place it in
.claude/skills/just/SKILL.mdinside your project - Restart your AI agent — it will auto-discover the skill
How just Compares
| Feature / Agent | just | Standard Approach |
|---|---|---|
| Platform Support | Claude | Limited / Varies |
| Context Awareness | High | Baseline |
| Installation Complexity | easy | N/A |
Frequently Asked Questions
What does this skill do?
Use `just` to save and run project-specific commands. Use when the user mentions `justfile`, `recipe`, or needs a simple alternative to `make` for task automation.
Which AI agents support this skill?
This skill is designed for Claude.
How difficult is it to install?
The installation complexity is rated as easy. You can find the installation instructions above.
Where can I find the source code?
You can find the source code on GitHub using the link provided at the top of the page.
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SKILL.md Source
# Just Command Runner
[GitHub Repository](https://github.com/casey/just)
`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](examples/node-docker.just)
- [Python + Venv](examples/python-venv.just)
- [Bun + TypeScript](examples/bun-typescript.just)
- [Astral UV + Python](examples/uv-python.just)
- [Multi-Module / Advanced](examples/multi-module.just)
## Workflow
1. **Create a `justfile`**:
Define recipes at the top level of your project. **Always include a `default` recipe that lists available commands:**
```just
default:
@just --list
```
```just
# 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.
```just
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:
```
Create a justfile for my Node project to handle lint, test, and dev
```
You would:
1. Create a `justfile`:
```just
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:
```
Add a recipe to just to deploy to a specific environment
```
You would:
1. Edit the `justfile`:
```just
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:
```
What commands are available in this project?
```
You would:
1. Run `just --list` to see available recipes and their comments.Related Skills
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