bash-defensive-patterns Skill (wshobson) for Claude Code

• set -Eeuo pipefail and what each flag does

  SKILL.md puts strict mode first in its best practices list. details.md has a Strict Mode section.

  Strict mode

• trap handlers that report errors and clean up

  Core principle 2 in details.md shows trapping errors and exit to run cleanup.

  Error trapping and cleanup

• Quoting, required variables and safe array loops

  Shows wrong and correct quoting, failing with a message when a required variable is unset, and reading command output into an array safely.

  Variable and array safety

• Find where the script lives

  Fundamental pattern 1.

  Script directory detection

• Prefixed functions with docs and error handling

  Pattern 2 gives a function layout with a naming prefix and checks.

  Function template

• mktemp directory plus trap cleanup

  Pattern 3 creates a temporary directory and removes it on exit.

  Files · Safe temp files

• Defaults, flags and required-argument checks

  Pattern 4.

  Argument parsing

• Timestamped log levels

  Pattern 5.

  Structured logging

• Background jobs, signals and wait

  Pattern 6 tracks background process IDs and waits for them.

  Runs code · Process orchestration

• No-overwrite moves, guarded cleanup and atomic writes

  Pattern 7 includes a safe directory cleanup example.

  Files · Safe file operations

• Scripts that are safe to rerun, and $() handling

  Patterns 8 and 9.

  Idempotent design and safe substitution

Watch out for

• Examples include file deletion and cleanup

  details.md has a safe directory cleanup example and mktemp cleanup traps. Check the paths in any script Claude writes before you run it. github.com

Security advisories