Error Handling in Bash

Overview

Bash error handling is explicit and must be designed carefully to avoid silent failures in production automation.

Defensive Controls

• set -euo pipefail
• trap handlers for cleanup and diagnostics
• Exit code checks after critical commands
• Structured stderr logging

flowchart TD
    A[Run Command] --> B{Exit code 0?}
    B -->|Yes| C[Continue]
    B -->|No| D[Log Error]
    D --> E[Cleanup]
    E --> F[Exit Non-Zero]

Practical Example

#!/usr/bin/env bash
set -euo pipefail
trap 'echo "Error on line $LINENO" >&2' ERR

cp config.yaml /etc/myapp/config.yaml
systemctl restart myapp

Production Example

A deployment script should fail fast on migration errors and stop rollout before traffic switching.

Common Pitfalls

• Assuming set -e handles every failure scenario
• Ignoring subshell and pipeline error behavior
• Missing cleanup handlers for temporary files

Key Takeaways

• Bash reliability depends on explicit failure control.
• trap and exit-code checks improve diagnosability.
• Fail-fast behavior protects production rollouts.