Bash Defensive Patterns

When to use this skill

Use Bash Defensive Patterns when an AI agent needs a reusable SKILL.md workflow for this job: Master defensive Bash programming techniques for production-grade scripts. Use when writing robust shell scripts, CI/CD pipelines, or system utilities requiring fault tolerance and safety.

When not to use it

Skip Bash Defensive Patterns when the task is outside the coding category, or when a more specific skill in this directory already covers the same workflow with clearer triggers.

How to install

1. Personal install: create ~/.claude/skills/bash-defensive-patterns/SKILL.md (and any bundled scripts) so Claude Code, Claude Desktop, and compatible agents can load it in every project.
2. Project install: commit the same folder at .claude/skills/bash-defensive-patterns/ so teammates get the skill with the repo.
3. Restart the agent session after copying files so it re-scans the skills directory, then ask for the task in words that match the skill description.

Full install guide for Claude, Cursor, and Codex

What this skill does

# Bash Defensive Patterns

Comprehensive guidance for writing production-ready Bash scripts using defensive programming techniques, error handling, and safety best practices to prevent common pitfalls and ensure reliability.

## When to Use This Skill

- Writing production automation scripts - Building CI/CD pipeline scripts - Creating system administration utilities - Developing error-resilient deployment automation - Writing scripts that must handle edge cases safely - Building maintainable shell script libraries - Implementing comprehensive logging and monitoring - Creating scripts that must work across different platforms

## Detailed patterns and worked examples

Detailed pattern documentation lives in `references/details.md`. Read that file when the navigation tier above is insufficient.

## Best Practices Summary

1. **Always use strict mode** - `set -Eeuo pipefail` 2. **Quote all variables** - `"$variable"` prevents word splitting 3. **Use [[]] conditionals** - More robust than [ ] 4. **Implement error trapping** - Catch and handle errors gracefully 5. **Validate all inputs** - Check file existence, permissions, formats 6. **Use functions for reusability** - Prefix with meaningful names 7. **Implement structured logging** - Include timestamps and levels 8. **Support dry-run mode** - Allow users to preview changes 9. **Handle temporary files safely** - Use mktemp, cleanup with trap 10. **Design for idempotency** - Scripts should be safe to rerun 11. **Document requirements** - List dependencies and minimum versions 12. **Test error paths** - Ensure error handling works correctly 13. **Use `command -v`** - Safer than `which` for checking executables 14. **Prefer printf over echo** - More predictable across systems

Intended uses

• Writing production automation scripts
• Building CI/CD pipeline scripts
• Creating system administration utilities
• Developing error-resilient deployment automation
• Writing scripts that must handle edge cases safely
• Building maintainable shell script libraries
• Implementing comprehensive logging and monitoring
• Creating scripts that must work across different platforms