The core difference is that: - `[` is treated as a statement - `[[` is treated as an expression Which, for example, is why you can't use `>` in `[` based exp

The core difference is that: - `[` is treated as a statement - `[[` is treated as an expression Which, for example, is why you can't use `>` in `[` based expressions. Bash thinks you want to redirect the output of `[` to somewhere else. This restriction is lifted for `[[` and makes for much more natural looking code.