shell-scripting-patternslisted

# Shell Scripting Patterns Best practices for bash/zsh scripts, with specific patterns for Claude Code hooks and dotfiles maintenance on macOS. ## Script Header & Strict Mode Every bash script starts with: ```bash #!/bin/bash set -euo pipefail ``` - `-e` exits on error, `-u` errors on undefined variables, `-o pipefail` makes a pipeline fail if any stage fails - Why: without these, a failed `cd` or a typo'd variable silently continues and corrupts state downstream When a non-zero exit is expected (grep finding nothing, optional commands), handle it explicitly instead of dropping strict mode: ```bash # grep returns 1 on no-match — don't let -e kill the script matches=$(grep -c "pattern" file || true) if ! command -v terminal-notifier >/dev/null 2>&1; then # fallback path fi ``` Note: hooks in this repo intentionally use `set -e` without `-u`/`pipefail` when they must be fail-open (see Hook Patterns below). Choose deliberately, not by omission. ## Quoting Quote every expansion unless you explicitly want word splitting: ```bash # ❌ WRONG: breaks on spaces, runs glob expansion rm $FILE_PATH [ -f $FILE_PATH ] && cat $FILE_PATH # ✅ CORRECT rm "$FILE_PATH" [[ -f "$FILE_PATH" ]] && cat "$FILE_PATH" ``` - Prefer `[[ ]]` over `[ ]` in bash: no word splitting inside, supports `=~` regex and `&&`/`||` - Use `"$@"` (never `$@` or `$*`) to forward arguments ## Variables & Functions ```bash # Defaults for optional values (plays well with set -u) timeout="${3:-5}" LOG_DIR="$