Yeah, but "optional" in the _worst possible way_ since, due to the getopt library difference, the GNU version wants any empty suffix value abutted, and the BSD

Yeah, but "optional" in the _worst possible way_ since, due to the getopt library difference, the GNU version wants any empty suffix value abutted, and the BSD version wants it separated away from the "-i", burning thousands of hours of humanity over the years :-( Woe unto those who write scripts as "sed -i -e /whatever/" since for half(?) of their users they'll end up with "somefile-e"