CLI Developer

Purpose

Provides expertise in building robust, user-friendly command-line applications and terminal interfaces. Covers argument parsing, interactive prompts, TUI frameworks, and shell automation across multiple languages.

When to Use

• Building CLI applications in any language
• Creating interactive terminal user interfaces
• Implementing command-line argument parsing
• Building shell scripts and automation tools
• Adding progress bars, spinners, and colors
• Creating REPL-style applications
• Distributing CLI tools as packages

Quick Start

Invoke this skill when:

• Building CLI applications in any language
• Creating interactive terminal user interfaces
• Implementing command-line argument parsing
• Building shell scripts and automation tools
• Creating REPL-style applications

Do NOT invoke when:

• Building GUI desktop applications (use windows-app-developer)
• Creating web-based interfaces (use frontend skills)
• Writing PowerShell-specific tools (use powershell skills)
• Building mobile applications (use mobile-developer)

Decision Framework

CLI Framework Selection:
├── Node.js → Commander.js, Yargs, Oclif
├── Python → Click, Typer, argparse
├── Go → Cobra, urfave/cli
├── Rust → Clap, structopt
├── TUI needed
│   ├── Node.js → Ink, Blessed
│   ├── Python → Textual, Rich
│   ├── Go → Bubbletea, tview
│   └── Rust → Ratatui, crossterm
└── Simple script → Shell (bash/zsh)

Core Workflows

1. CLI Application Setup

1. Choose framework based on language/needs
2. Define command structure and subcommands
3. Implement argument and option parsing
4. Add input validation and help text
5. Implement core command logic
6. Add output formatting (JSON, table, etc.)
7. Package for distribution

2. Interactive TUI Development

1. Select TUI framework
2. Design screen layout and components
3. Implement input handling and navigation
4. Add state management
5. Handle terminal resize events
6. Test across different terminal emulators

3. CLI Distribution

1. Add proper versioning
2. Create man pages or help docs
3. Package for target platforms
4. Set up installation via package managers
5. Create shell completions
6. Add update mechanism

Best Practices

• Follow POSIX conventions for flags and arguments
• Provide both short (-v) and long (--verbose) options
• Include --help and --version flags
• Use exit codes properly (0 for success)
• Support piping and stdin input
• Add shell completion scripts

Anti-Patterns

Anti-Pattern	Problem	Correct Approach
No help text	Users can't discover commands	Add comprehensive --help
Silent failures	Users don't know what went wrong	Clear error messages + exit codes
Hard-coded paths	Breaks on other systems	Use environment variables, XDG
No stdin support	Can't pipe data	Support reading from stdin
Colored output to pipes	Breaks parsing	Detect TTY, disable colors for pipes