The README say, early on, that it recommends using the -w flag with the -i flag. So I tried that immediately. That led to errors and I started wondering whether flags most go in a particular position within the command. After a while I read more of the README and discovered that -i takes an argument of its own. Arguably, here we have a PEBCAK. But there is the following problem. So far as I can see, the README does not actually explain that argument or, more precisely, its different possible values.