Testing Traps

- `[ $var = "x" ]` fails if var empty — quote: `[ "$var" = "x" ]` - `[[ ]]` doesn't word-split — `[[ $var = "x" ]]` works unquoted - `<` and `>` in `[ ]` are redirects — use `-lt`, `-gt` or escape - Pattern only in `[[ ]]` — `[[ $var == *.txt ]]` - Pattern must be unquoted — `"*.txt"` matches literal asterisk