Today when I reviewed our project's source code, I found there are lots of unnecessary "spaces" and "tabs" located at each line's end. So I decided to delete them with regular expression.
However, I found the command
sed -i '/\s+$/d' doesn't work. Until I changed the command to
see -ri '/\s+$/d', it acted as my expectation. From the manual of
sed, it said
-r invokes extended regexp.
I'm confused, why there are so many regexp variants? Like vim/emacs/perl/sed regexp. Why can't the regexp offer an unique user interface?