sed line range, all but the last line

Question

You can specify a range of lines to operate on. For example, to operate on all lines, (which is of course the default):

sed -e "1,$ s/a/b/"

But I need to operate on all but the last line. You apparently can't use arithmetic expressions:

sed -e "1,$-1 s/a/b/"

(I am using cygwin in this case, if it makes a difference)

Answer 1

sed -e "$ ! s/a/b/"

This will match every line but the last. Confirmed with a quick test!