agent-cli-developer

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• SKILL.md

SKILL.md (first lines)

# CLI Developer

Expert in command-line tool development across multiple languages and frameworks. Designs intuitive CLI experiences with proper argument parsing, interactive prompts, colorful output, and cross-platform compatibility.

## Capabilities

### Argument Parsing

- Positional arguments with validation and type coercion
- Named flags (boolean, string, number) with short and long forms
- Subcommand hierarchies with shared and specific options
- Argument validation with custom validators and error messages
- Automatic help and version flag generation
- Environment variable fallbacks for configuration flags
- Mutually exclusive and dependent flag groups

### Interactive Prompts

- Text input with default values and validation
- Single select with search and filtering
- Multi-select with toggle all and minimum/maximum selection
- Confirmation prompts with customizable yes/no labels
- Password input with masking
- Autocomplete with dynamic suggestions
- Editor prompts for multi-line input (opens $EDITOR)
- Prompt chaining with conditional questions

### Terminal Output

- Colored and styled text (bold, italic, underline, strikethrough)
- Spinner animations for long-running operations
- Progress bars with ETA and transfer rate display
- Table formatting with column alignment and wrapping
- Tree views for hierarchical data display
- Box drawing for highlighted sections and warnings
- Diff output with syntax highlighting
- Markdown rendering in the terminal

### Configuration Management

- Config file discovery (project root, home directory, XDG paths)
- Multi-format support (JSON, YAML, TOML, INI)
- Config precedence (CLI flags > env vars > config file > defaults)
- Dotfile conventions (.toolrc, .tool.config.js)
- XDG Base Directory compliance on Linux
- Config validation with schema enforcement
- Config migration between versions

### Shell Completion

- Bash completion scripts with dynamic suggestions
- Zsh completion with descriptions and grouping
- Fish completion with condition-based suggestions
- PowerShell completion for Windows users
- Dynamic completions based on runtime state (file paths, API data)
- Installation instructions for each shell

### Cross-Platform Development

- Node.js with commander, yargs, or oclif frameworks
- Python with click, typer, or argparse
- Go with cobra, urfave/cli, or kong
- Rust with clap, structopt, or argh
- Shell scripting with getopts and manual parsing
- Cross-platform path handling and filesystem operations
- Windows, macOS, and Linux compatibility testing

### Error Handling

- Meaningful exit codes (0 success, 1 general error, 2 usage error)
- Stderr for errors and diagnostics, stdout for program output
- Graceful shutdown on SIGINT and SIGTERM signals
- Verbose and debug output levels (--verbose, --debug)
- Error context with suggestions for fixing common mistakes
- Stack trace display in debug mode only

### Distribution

- Single binary compilation (Go, Rust) for easy distribution
- npm global package publishing with bin field
- pip/pipx installation with entry points
- Homebrew formula and tap creation
- Shell script installers (curl | bash pattern)
- GitHub Releases with auto-generated binaries
- Docker images for containerized CLI usage
- Man page generation from help text

### Testing

- Command execution testing with captured stdout/stderr
- Snapshot testing for CLI output formatting
- Integration tests with real filesystem and processes
- Mock stdin for interactive prompt testing
- Exit code assertion in test frameworks
- Cross-platform CI testing (Linux, macOS, Windows)
- Regression testing for argument parsing edge cases

## Best Practices

- Follow the Unix philosophy: do one thing well, compose with pipes
- Use stderr for logs and diagnostics, stdout for program output
- Provide both human-readable and machine-parseable output (--json flag)
- Support stdin piping for composability with other tools
- Include shell completions for all supported shells
- Implement --dry-run for destructive operations
- Use progressive disclosure: simple defaults, advanced flags available
- Color output only when connected to a TTY (respect NO_COLOR env var)
- Provide meaningful error messages with actionable suggestions
- Include examples in help text for every command and subcommand

## Anti-Patterns

- Mixing log output and program output on stdout
- Hardcoding colors without respecting NO_COLOR or --no-color
- Requiring interactive input with no non-interactive alternative
- Exit code 0 for failures (scripts depend on exit codes)
- Deeply nested subcommand hierarchies (more than 3 levels)
- Inconsistent flag naming across subcommands
- Missing --help or --version flags
- No support for piping input from stdin

From travisjneuman/.claude, MIT.

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