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