just - Command Runner

IMPORTANT:

just

is the PREFERRED command runner for project task automation. Use Justfiles instead of Makefiles for new projects and task automation.

Core Philosophy

Justfiles over Makefiles: Prefer just for task automation unless working with existing Make-based projects
Simple recipes: Keep recipe definitions concise and readable
Delegate to scripts: For complex logic, call external scripts rather than embedding in recipes
Just as orchestrator: Use just to coordinate and invoke scripts, not to contain business logic

Basic Usage Patterns

Running Recipes

bash

# List available recipes
just --list
just -l

# Run a recipe
just build
just test

# Run recipe with arguments
just deploy production
just run-test integration

# Run recipe from different directory
just --working-directory /path/to/project build

# Choose a different Justfile
just --justfile custom.just build

Recipe Definition Basics

just

# Simple recipe
build:
    cargo build --release

# Recipe with description (shown in --list)
# Run all tests
test:
    cargo test --quiet

# Recipe with dependencies (runs setup first)
deploy: build test
    ./scripts/deploy.sh

# Recipe with parameters
run-test test_name:
    cargo test {{test_name}}

# Recipe with default parameter value
serve port="8080":
    python -m http.server {{port}}

# Recipe with multiple parameters
deploy env branch="main":
    ./scripts/deploy.sh {{env}} {{branch}}

Delegation Pattern (PREFERRED)

Good - Delegates to script:

just

# Build the project
build:
    ./scripts/build.sh

# Run integration tests
test-integration:
    ./scripts/test-integration.sh

# Deploy to environment
deploy env:
    ./scripts/deploy.sh {{env}}

Avoid - Complex logic in recipe:

just

# ❌ Too complex - should be in a script
deploy env:
    #!/usr/bin/env bash
    set -euo pipefail
    if [ "{{env}}" = "production" ]; then
        echo "Deploying to production..."
        git fetch origin
        git checkout main
        git pull
        docker build -t app:latest .
        docker push registry.example.com/app:latest
        kubectl apply -f k8s/production/
        kubectl rollout status deployment/app
    else
        echo "Deploying to staging..."
        # ... many more lines ...
    fi

Better - Simple orchestration:

just

# Deploy to production
deploy-prod:
    ./scripts/deploy.sh production

# Deploy to staging
deploy-staging:
    ./scripts/deploy.sh staging

# Generic deploy with validation
deploy env:
    ./scripts/validate-env.sh {{env}}
    ./scripts/deploy.sh {{env}}

Recipe Features

Dependencies

just

# Recipe runs after its dependencies
all: clean build test deploy

# Dependencies run in order specified
deploy: build test package
    ./scripts/deploy.sh

# Multiple dependency chains
full-deploy: lint build test docker-build docker-push k8s-deploy

Variables

just

# Set variables at top of file
version := "1.2.3"
registry := "registry.example.com"
image := registry + "/app:" + version

# Use in recipes
docker-build:
    docker build -t {{image}} .

docker-push:
    docker push {{image}}

# Environment variables
deploy:
    API_KEY=$API_KEY ./scripts/deploy.sh

Conditional Execution

just

# Use shell conditionals in scripts
test:
    ./scripts/test.sh

# Or delegate to script
check-and-test:
    ./scripts/check-and-test.sh

Private Recipes

just

# Private recipe (not shown in --list, can't be run directly)
_setup:
    ./scripts/setup-env.sh

# Public recipe uses private recipe
deploy: _setup
    ./scripts/deploy.sh

Recipe Attributes

just

# Ignore errors (continue even if fails)
[ignore-errors]
lint:
    ./scripts/lint.sh

# Run in specific directory
[working-directory: 'frontend']
build-ui:
    npm run build

# Confirm before running
[confirm]
deploy-prod:
    ./scripts/deploy.sh production

# Don't print recipe before running
[no-quiet]
status:
    ./scripts/status.sh

Common Patterns

Development Workflow

just

# Default recipe (runs when you type 'just')
default: check test

# Quick validation
check:
    ./scripts/check.sh

# Run all tests
test:
    ./scripts/test.sh

# Full CI workflow
ci: check test lint build

Build Automation

just

# Clean build artifacts
clean:
    ./scripts/clean.sh

# Build project
build:
    ./scripts/build.sh

# Full rebuild
rebuild: clean build

# Build with caching
build-cached:
    ./scripts/build.sh --cache

Multi-Environment Deployment

just

# Development environment
dev:
    ./scripts/run-dev.sh

# Staging deployment
deploy-staging:
    ./scripts/deploy.sh staging

# Production deployment (with confirmation)
[confirm]
deploy-prod:
    ./scripts/deploy.sh production

# Deploy to any environment
deploy env:
    ./scripts/validate-env.sh {{env}}
    ./scripts/deploy.sh {{env}}

Docker Workflows

just

# Build Docker image
docker-build:
    ./scripts/docker-build.sh

# Run container locally
docker-run:
    ./scripts/docker-run.sh

# Push to registry
docker-push: docker-build
    ./scripts/docker-push.sh

# Complete Docker workflow
docker: docker-build docker-push

Database Operations

just

# Run migrations
migrate:
    ./scripts/db-migrate.sh

# Rollback migration
migrate-rollback:
    ./scripts/db-rollback.sh

# Seed database
seed:
    ./scripts/db-seed.sh

# Reset database (dev only)
[confirm]
db-reset:
    ./scripts/db-reset.sh

Script Organization

Recommended Structure

project/
├── justfile
├── scripts/
│   ├── build.sh
│   ├── test.sh
│   ├── deploy.sh
│   ├── validate-env.sh
│   └── utils/
│       ├── common.sh
│       └── logging.sh
└── src/
    └── ...

Script Best Practices

Make scripts executable:

bash

chmod +x scripts/*.sh

Use shebang in scripts:

bash

#!/usr/bin/env bash
set -euo pipefail

# Script logic here

Keep scripts focused:

bash

# Good - single purpose
# scripts/build.sh
#!/usr/bin/env bash
set -euo pipefail

echo "Building project..."
cargo build --release

Source common utilities:

bash

# scripts/deploy.sh
#!/usr/bin/env bash
set -euo pipefail

source "$(dirname "$0")/utils/common.sh"
source "$(dirname "$0")/utils/logging.sh"

log_info "Starting deployment..."
# Deployment logic

Advanced Features

Command Evaluation

just

# Backticks execute shell commands
commit := `git rev-parse --short HEAD`
timestamp := `date +%Y%m%d-%H%M%S`

# Use in recipes
tag:
    echo "Tagging {{commit}} at {{timestamp}}"

Multi-line Constructs

just

# Multi-line variables
help := '''
  Available commands:
    build  - Build the project
    test   - Run tests
    deploy - Deploy to production
'''

# Print help
help:
    @echo {{help}}

Settings

just

# Change shell (default is sh)
set shell := ["bash", "-c"]

# Make all recipes silent (@echo becomes echo)
set quiet := true

# Use PowerShell on Windows
set windows-shell := ["powershell.exe", "-c"]

# Use Python for recipes
set shell := ["python3", "-c"]

Imports

just

# Import recipes from other files
import 'ci.just'
import 'deploy.just'

# Use imported recipes
all: ci-check deploy-staging

Integration with Other Tools

With Cargo (Rust)

just

# Rust development workflow
check:
    cargo check --quiet

test:
    cargo test --quiet

clippy:
    cargo clippy

build: check test clippy
    cargo build --release

# Or delegate to script
rust-workflow:
    ./scripts/rust-workflow.sh

With npm/pnpm/yarn

just

# Install dependencies
install:
    pnpm install

# Run dev server
dev:
    pnpm run dev

# Build frontend
build:
    pnpm run build

# Or use scripts
ui-build:
    ./scripts/build-ui.sh

With Docker

just

# Docker operations via scripts
docker-build:
    ./scripts/docker/build.sh

docker-run:
    ./scripts/docker/run.sh

docker-compose-up:
    docker-compose up -d

With Git

just

# Git workflow helpers
sync:
    git fetch origin
    git pull

push: test
    git push origin main

release version:
    ./scripts/release.sh {{version}}

Complete Workflow Examples

Workflow 1: Web Application

just

# Default - run dev server
default: dev

# Install dependencies
install:
    ./scripts/install.sh

# Development server
dev:
    ./scripts/dev.sh

# Run tests
test:
    ./scripts/test.sh

# Build for production
build:
    ./scripts/build.sh

# Deploy to staging
deploy-staging: test build
    ./scripts/deploy.sh staging

# Deploy to production
[confirm]
deploy-prod: test build
    ./scripts/deploy.sh production

Workflow 2: Rust Project

just

# Default - check code
default: check

# Fast check
check:
    cargo check --quiet

# Run tests
test:
    cargo test --quiet

# Lint code
lint:
    cargo clippy

# Full validation
ci: test lint
    ./scripts/verify-formatting.sh

# Build release
build:
    cargo build --release

# Install binary
install: build
    cargo install --path .

Workflow 3: Monorepo

just

# Build all services
build-all:
    ./scripts/build-all.sh

# Test all services
test-all:
    ./scripts/test-all.sh

# Build specific service
build-service service:
    ./scripts/build-service.sh {{service}}

# Deploy specific service
deploy service env:
    ./scripts/deploy-service.sh {{service}} {{env}}

# Full deployment
deploy-all env: test-all build-all
    ./scripts/deploy-all.sh {{env}}

Common Commands Quick Reference

bash

# List recipes
just --list

# Run recipe
just <recipe>

# Run with arguments
just <recipe> arg1 arg2

# Set variable
just var=value recipe

# Choose Justfile
just --justfile path/to/justfile recipe

# Work in different directory
just --working-directory /path recipe

# Dry run (show what would run)
just --dry-run recipe

# Verbose output
just --verbose recipe

# Choose recipe interactively
just --choose

Best Practices Summary

Keep recipes simple: 1-3 lines max; delegate complex logic to scripts
Use descriptive names:
```
deploy-prod
```
not
```
dp
```
,
```
test-integration
```
not
```
ti
```
Add comments: Describe what each recipe does
Organize scripts: Keep scripts in
```
scripts/
```
directory with logical subdirectories
Make scripts executable: Use
```
chmod +x scripts/*.sh
```
Use dependencies: Chain recipes with dependencies rather than duplicating commands
Confirm destructive operations: Use
```
[confirm]
```
for deployments, database resets, etc.
Private recipes for setup: Use
```
_recipe
```
naming for internal setup steps
Default recipe: Provide sensible default (usually
```
dev
```
or
```
check
```
)
Document in comments: Add comments explaining complex workflows

When to Use Scripts vs. Recipes

Use Recipe Directly:

Single command execution
Simple chaining (3 commands or less)
Setting environment variables for a command
Quick aliases

Use Script (PREFERRED for most cases):

Complex conditional logic
Multiple steps with error handling
Reusable logic across recipes
Long command sequences (>3 commands)
Anything requiring significant bash scripting

Justfile Template

just

# Set shell for all recipes
set shell := ["bash", "-c"]

# Variables
version := "1.0.0"

# Default recipe
default: check

# List all recipes
help:
    @just --list

# Development
dev:
    ./scripts/dev.sh

# Testing
test:
    ./scripts/test.sh

# Build
build:
    ./scripts/build.sh

# Full CI check
ci: test build
    ./scripts/verify.sh

# Deploy to staging
deploy-staging: ci
    ./scripts/deploy.sh staging

# Deploy to production
[confirm]
deploy-prod: ci
    ./scripts/deploy.sh production

# Clean build artifacts
clean:
    ./scripts/clean.sh

Migration from Make

Key Differences from Make

Not a build system: just is for running commands, not tracking file dependencies
Recipes always run: Unlike Make targets, recipes run every time (no file timestamp checking)
Simpler syntax: No need for
```
.PHONY
```
, tabs vs. spaces issues, etc.
Better error messages: Clear, helpful error output

Converting Makefile to Justfile

Makefile:

make

.PHONY: build test deploy

build:
	cargo build --release

test:
	cargo test

deploy: build test
	./deploy.sh

Justfile:

just

build:
    cargo build --release

test:
    cargo test

deploy: build test
    ./scripts/deploy.sh

Resources

Official documentation: https://just.systems
GitHub repository: https://github.com/casey/just
Installation:
```
brew install just
```
(macOS) or
```
cargo install just
```

just

NPX Install

Tags

SKILL.md Content

just - Command Runner

Core Philosophy

Basic Usage Patterns

Running Recipes

Recipe Definition Basics

Delegation Pattern (PREFERRED)

Recipe Features

Dependencies

Variables

Conditional Execution

Private Recipes

Recipe Attributes

Common Patterns

Development Workflow

Build Automation

Multi-Environment Deployment

Docker Workflows

Database Operations

Script Organization

Recommended Structure

Script Best Practices

Advanced Features

Command Evaluation

Multi-line Constructs

Settings

Imports

Integration with Other Tools

With Cargo (Rust)

With npm/pnpm/yarn

With Docker

With Git

Complete Workflow Examples

Workflow 1: Web Application

Workflow 2: Rust Project

Workflow 3: Monorepo

Common Commands Quick Reference

Best Practices Summary

When to Use Scripts vs. Recipes

Use Recipe Directly:

Use Script (PREFERRED for most cases):

Justfile Template

Migration from Make

Key Differences from Make

Converting Makefile to Justfile

Resources