On my machine, (Ubuntu 14.04) look only performs a binary search if the "-b" option is passed (unless no file is specified, in which case it behaves as describe

On my machine, (Ubuntu 14.04) look only performs a binary search if the "-b" option is passed (unless no file is specified, in which case it behaves as described in the linked manpage). My manpage notes in the compatibility section: look uses a linear search by default instead of a binary search, which is what most other implementations use by default.