Bash Defensive Patterns

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

• Always use strict mode - set -Eeuo pipefail
• Quote all variables - "$variable" prevents word splitting
• Use [[]] conditionals - More robust than [ ]
• Implement error trapping - Catch and handle errors gracefully
• Validate all inputs - Check file existence, permissions, formats
• Use functions for reusability - Prefix with meaningful names
• Implement structured logging - Include timestamps and levels
• Support dry-run mode - Allow users to preview changes
• 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