Building CLIs

Build professional command-line interfaces across Python, Go, and Rust using modern frameworks with robust argument parsing, configuration management, and shell integration.

When to Use This Skill

Use this skill when:

• Building developer tooling or automation CLIs
• Creating infrastructure management tools (deployment, monitoring)
• Implementing API client command-line tools
• Adding CLI capabilities to existing projects
• Packaging utilities for distribution (PyPI, Homebrew, binary releases)

Common triggers: "create a CLI tool", "build a command-line interface", "add CLI arguments", "parse command-line options", "generate shell completions"

Framework Selection

Quick Decision Guide

Python Projects:

• Typer (recommended): Modern type-safe CLIs with minimal boilerplate
• Click: Mature, flexible CLIs for complex command hierarchies

Go Projects:

• Cobra (recommended): Industry standard for enterprise tools (Kubernetes, Docker, GitHub CLI)
• urfave/cli: Lightweight alternative for simple CLIs

Rust Projects:

• clap v4 (recommended): Type-safe with derive API or builder API for runtime flexibility

For detailed framework comparison and selection criteria, see references/framework-selection.md.

Core Patterns

Arguments vs. Options vs. Flags

Positional Arguments:

• Primary input, identified by position
• Use for required inputs (max 2-3 arguments)
• Example: convert input.jpg output.png

Options:

• Named parameters with values
• Use for configuration and optional inputs
• Example: --output file.txt, --config app.yaml

Flags:

• Boolean options (presence = true)
• Use for switches and toggles
• Example: --verbose, --dry-run, --force

Decision Matrix: