Hello World

The simplest AIRun script - your first executable prompt

The simplest possible AIRun script. This example shows the basic shebang syntax and how to make a markdown file executable.

The Script

#!/usr/bin/env -S ai --haiku
Say hello and briefly explain what you can do.

This is the complete script from examples/hello.md. It’s only 2 lines!

How It Works

The Shebang Line

#!/usr/bin/env -S ai --haiku

This line tells your system how to run the file:

• #!/usr/bin/env - Standard Unix shebang for finding executables in PATH
• -S - Essential flag that allows passing arguments (like --haiku) to the command
• ai - The AIRun command
• --haiku - Use the fastest, cheapest model tier (perfect for simple tasks)

You must use -S when passing flags in a shebang. Without it, env treats ai --haiku as a single command name and fails.

Works: #!/usr/bin/env -S ai --haiku

Fails: #!/usr/bin/env ai --haiku

The Prompt

Everything after the shebang is your prompt:

Say hello and briefly explain what you can do.

No special syntax needed - just write what you want the AI to do.

Running the Script

Method 1: Make it executable and run directly

# Make the file executable
chmod +x hello.md

# Run it
./hello.md

The shebang tells your system to use ai --haiku to execute the file.

Method 2: Run with the ai command

# Shebang flags are still honored
ai hello.md

Method 3: Override the model

# Use Sonnet instead of Haiku (CLI overrides shebang)
ai --sonnet hello.md

# Use a different provider
ai --aws --opus hello.md

Flag precedence: CLI flags > shebang flags > saved defaults

Running ai --sonnet hello.md overrides the --haiku in the shebang.

Why Use Haiku?

This script uses --haiku because:

• Fastest - Haiku responds in milliseconds
• Cheapest - Lowest cost per token
• Sufficient - Simple text generation doesn’t need Opus

Model selection guide:

Task	Model
Simple text, greetings, summaries	--haiku
Code analysis, test running	--sonnet
Complex reasoning, architecture design	--opus

Creating Your Own

Create a new script:

cat > greet.md << 'EOF'
#!/usr/bin/env -S ai --haiku
Write a friendly greeting and tell me a fun fact about AI.
EOF

chmod +x greet.md
./greet.md

Read-Only by Default

This script doesn’t need any permission flags because it only generates text. It cannot:

• Write files
• Run commands
• Modify your system

For scripts that need to take actions, see:

• Test Automation - Using --skip for running commands
• Code Analysis - Read-only analysis without permissions

Next Steps

Code Analysis

Analyze codebases without modifying anything

Variables

Add customizable parameters to scripts

Test Automation

Run commands and report results

Scripting Guide

Complete guide to executable markdown