bash-defensive-patterns

Start every script with set -Eeuo pipefail to exit on errors, undefined variables, and pipe failures. Add trap handlers for ERR and EXIT to log failures and clean up temporary files, and quote all variable expansions to prevent word splitting.

set -e exits the script when any command returns non-zero, set -u treats unset variables as errors, and set -o pipefail makes a pipeline fail if any command in it fails. Adding set -E ensures ERR traps are inherited inside functions.

Use [[ ]] for Bash-specific scripts because it avoids word splitting and pathname expansion, and supports && and || natively. Use [ ] only when POSIX portability across different shells is required.

Use a while loop with a case statement over $1, shifting after each option, and handle --help, unknown options, and the -- terminator explicitly. Validate required arguments after parsing and fail with a usage message when they are missing.

Unquoted variables undergo word splitting, so paths with spaces break into multiple arguments. Always quote expansions like "$file" and use find with -print0 plus read -d '' for NUL-safe iteration over filenames.

Design for idempotency by checking whether resources already exist before creating them, such as testing for directories with [[ -d ]] before mkdir. Combine this with dry-run support so users can preview changes before execution.