UNIX/POSIX Standards CLI Best Practices

Comprehensive guidelines for building command-line tools that follow UNIX conventions, designed for AI agents and LLMs. Contains 44 rules across 8 categories, prioritized by impact from critical (argument handling, exit codes, output streams) to incremental (configuration and environment).

When to Apply

Reference these guidelines when:

• Writing new CLI tools in any language
• Parsing command-line arguments and flags
• Deciding what goes to stdout vs stderr
• Choosing appropriate exit codes
• Handling signals like SIGINT and SIGTERM

Rule Categories by Priority