Script Commands

When you think of powerful CLI tools - git, docker, kubectl - they all share a common pattern: they're organized around commands. You don't just run git with flags; you run git commit, git push, git branch - each a distinct operation with its own arguments.

Rad lets you build tools like this through first-class command support. You can define multiple commands in a single script, each with their own arguments and implementation.

Basic Syntax

Let's start with a very simple example:

#!/usr/bin/env rad

command greet:
    name str
    calls greet_user

fn greet_user():
    print("Hello, {name}!")

This script defines a single command called greet that takes a name argument.

Invoke it by specifying the command name followed by its arguments:

> ./script.rad greet Alice

Hello, Alice!

Let's break down the syntax:

1. command greet: - Defines a command named greet
2. name str - The command takes one required string argument called name
3. calls greet_user - Specifies which function to execute when this command runs
4. fn greet_user(): - Defines the function that implements the command logic (defined after commands)

Command arguments (like name) become script-wide variables, accessible throughout your script.

Multiple Commands

The power of commands emerges when you define several in one script. Let's create a simple deployment tool:

#!/usr/bin/env rad

command deploy:
    env str
    calls do_deploy

command status:
    env str
    calls do_status

fn do_deploy():
    print("Deploying to {env}...".yellow())
    print("Deployment complete!".green())

fn do_status():
    print("Checking status of {env}...".yellow())
    print("Environment {env} is healthy".green())

Now you can invoke either command:

> ./tool.rad deploy staging

Deploying to staging...
Deployment complete!

> ./tool.rad status production

Checking status of production...
Environment production is healthy

Each command has its own arguments and implementation, but they live in the same script and can share code.

Adding Descriptions

Commands should include descriptions to make your tool self-documenting. Use the familiar --- ... --- header syntax:

#!/usr/bin/env rad

command deploy:
    ---
    Deploy the application to an environment
    ---
    env str
    calls do_deploy

command status:
    ---
    Check the health of an environment
    ---
    env str
    calls do_status

fn do_deploy():
    print("Deploying to {env}...".yellow())

fn do_status():
    print("Environment {env} is healthy".green())

These descriptions appear in the help output:

> ./tool.rad -h

Usage:
  tool.rad [command] [OPTIONS]

Commands:
  deploy    Deploy the application to an environment
  status    Check the health of an environment

Notice how Rad automatically generates a usage string listing all available commands.

Multi-line descriptions

Just like script headers, command descriptions can span multiple lines:

command deploy:
    ---
    Deploy the application to an environment.
    This will build, test, and deploy your application.
    ---

Important: The first line appears in the script's overall help output, so keep it concise. Additional lines only appear when you request help for that specific command (./tool.rad deploy -h).

Command Arguments

Each command can define its own arguments using the same syntax you learned in Args. Let's expand our deployment tool:

#!/usr/bin/env rad

command deploy:
    ---
    Deploy the application to an environment
    ---
    env str              # Environment to deploy to
    branch str = "main"  # Branch to deploy from
    skip_tests bool      # Skip running tests before deploy
    calls do_deploy

fn do_deploy():
    if skip_tests:
        print("⚠️  Skipping tests".yellow())
    else:
        print("Running tests...".yellow())

    print("Deploying {branch} to {env}...".yellow())
    print("✅ Deployment complete!".green())

The arguments work exactly as they do in the args: block - you can use defaults, optional types, constraints, and comments for help text.

Invoke with positional arguments:

> ./tool.rad deploy staging feature-branch

Running tests...
Deploying feature-branch to staging...
✅ Deployment complete!

Or use flags (especially for booleans):

> ./tool.rad deploy --env=production --skip-tests

⚠️  Skipping tests
Deploying main to production...
✅ Deployment complete!

Shared Args

Often you want arguments that apply to all commands - like a --verbose flag or a --config path. Define these in an args: block to share them across commands:

#!/usr/bin/env rad

args:
    verbose v bool   # Enable verbose output
    config str = "~/.config/tool.yaml"

command deploy:
    ---
    Deploy the application
    ---
    env str
    calls do_deploy

command status:
    ---
    Check environment status
    ---
    env str
    calls do_status

fn do_deploy():
    if verbose:
        print("Config: {config}".yellow())
        print("Deploying to {env}...".yellow())
    print("✅ Deployed!".green())

fn do_status():
    if verbose:
        print("Config: {config}".yellow())
        print("Checking {env}...".yellow())
    print("Environment healthy".green())

Shared args are available to all commands:

> ./tool.rad deploy staging --verbose

Config: ~/.config/tool.yaml
Deploying to staging...
✅ Deployed!

> ./tool.rad status production --verbose

Config: ~/.config/tool.yaml
Checking production...
Environment healthy

Shared args are flag-only

When commands exist, shared args can only be passed as flags (like --verbose, -v, or --config=value), not positionally. This keeps the invocation clear: the first positional argument is always the command name.

Both long form (--verbose) and short form (-v) work for shared args.

Command-specific args can be positional or flags, just like regular script args.

Command Callbacks

We've been using function references (calls on_deploy), which is the recommended approach for most commands. However, for very short implementations, you can also use inline lambdas:

#!/usr/bin/env rad

command deploy:
    ---
    Deploy the application
    ---
    env str
    calls on_deploy

command rollback:
    ---
    Rollback a deployment
    ---
    env str
    calls fn():
        print("Rolling back {env}...".yellow())
        print("✅ Rollback complete!".green())

fn on_deploy():
    print("Deploying to {env}...".yellow())
    print("✅ Done!".green())

Shared Logic

You can write code after all command blocks that runs before any callback is invoked. This is useful for setup logic that all commands need:

#!/usr/bin/env rad

command deploy:
    env str
    calls on_deploy

command rollback:
    env str
    calls on_rollback

// This runs before any callback
print("Initializing...".yellow())
config = read_file("config.yaml")
print("Config loaded".green())

fn on_deploy():
    // config is available here
    print("Deploying to {env} using config...")

fn on_rollback():
    // config is available here too
    print("Rolling back {env}...")

When you run ./script.rad deploy staging, the flow is:

1. Parse arguments
2. Run shared logic (lines 12-14)
3. Run the callback (on_deploy)

This pattern is useful for loading configuration files, setting up connections, or validating preconditions that apply to all commands.

Getting Help

Rad automatically generates help documentation for your commands. There are two levels of help:

Script-level help shows all available commands:

> ./tool.rad -h

Usage:
  tool.rad [command] [OPTIONS]

Commands:
  deploy      Deploy the application
  rollback    Rollback a deployment
  status      Check environment status

Command-level help shows arguments for a specific command:

> ./tool.rad deploy -h

Deploy the application

Usage:
  deploy <env> [branch] [OPTIONS]

Command args:
      --env str       Environment to deploy to
      --branch str    Branch to deploy from (default "main")
      --skip-tests    Skip running tests before deploy
  -v, --verbose       Enable verbose output
      --config str    (default "~/.config/tool.yaml")

Notice how the help includes:

• The command description
• Required and optional arguments
• Default values
• Shared args (like --verbose and --config)
• Help text from # comments

Practical Example

Here's a concise, realistic example that demonstrates the "dev script" pattern - a common use case for replacing messy Makefiles or complex package.json script sections with a single, readable CLI entry point.

Dev Script

Instead of remembering different commands for building, testing, and running your project, you can wrap them in a single dev.rad script. This demonstrates shared arguments, boolean flags, and how to pass arguments down to underlying tools:

#!/usr/bin/env rad
---
Facilitates working with this repo's project.
---

args:
    verbose v bool   # Enable verbose output

command start:
    ---
    Start the local development server
    ---
    port int = 3000    # Port to listen on
    detach d bool      # Run in background
    calls on_start

command test:
    ---
    Run the test suite
    ---
    grep str?      # Filter tests by name
    watch w bool   # Re-run on file changes
    calls on_test

command build:
    ---
    Compile for production
    ---
    calls on_build

// Shared setup logic runs before any callback
if verbose:
    print("Checking project structure...".yellow())

if not path_exists("package.json"):
    print_err("Error: package.json not found".red())
    print_err("Run this script from the project root".yellow())
    exit(1)

fn on_start():
    print("🚀 Starting server on http://localhost:{port}...")

    cmd = "npm start -- --port {port}"

    if detach:
        $`{cmd} &`
        print("Server started in background".green())
    else:
        $`{cmd}`

fn on_test():
    opts = ""
    if watch:
        opts = "{opts} --watch"
    if grep: 
        opts = "{opts} -t '{grep}'"

    if verbose:
        print("Running: pytest {opts}".yellow())

    print("🧪 Running tests...")
    $`pytest {opts}` catch:
        print_err("Tests failed!".red())
        exit(1)

fn on_build():
    print("📦 Building for production...".yellow())

    $`rm -rf ./dist`
    $`npm run build` catch:
        print_err("Build failed".red())
        exit(1)

    print("✅ Build complete in ./dist".green())

Usage:

> ./dev.rad start
🚀 Starting server on http://localhost:3000...

> ./dev.rad start --port 8080 --detach
🚀 Starting server on http://localhost:8080...
Server started in background

> ./dev.rad test --grep "login_flow" --watch
🧪 Running tests...

> ./dev.rad build
📦 Building for production...
✅ Build complete in ./dist

Notice how this example uses:

• Shared args (--verbose) available to all commands
• Command-specific arguments with defaults (port, detach, grep, watch)
• Shared logic that runs before any callback
• Function references for callbacks (calls on_start, etc.)
• Integration with shell commands to wrap existing tools
• Clear, self-documenting help text

Summary

• Script commands partition scripts into operations using command name: blocks
• Each command has:
  • Its own arguments (using standard args syntax)
  • A description block (--- ... ---)
  • A callback implementation (function reference or inline lambda)
• Shared args (from args: block) are available to all commands
  • Must be passed as flags when commands exist
• Shared logic runs before any callback. Write code after command blocks for setup that all commands need.
• Help is automatic:
  • ./script -h lists available commands
  • ./script command -h shows command-specific help
• Callbacks:
  • Function references: calls function_name (recommended)
  • Inline lambdas: calls fn(): (for short implementations)
• Use script commands to build CLI tools, not just scripts

Next

Rad provides a powerful system for looking up values from predefined resource files, which is particularly useful for building interactive tools.

We'll explore this in the next section: Resources.