How to remove last directory from a path with sed?

Question

How to remove the last dir with sed (not dirname), like this:

echo "/dir1/dir2/dir3/dir4" | sed .....

So I would get /dir1/dir2/dir3.

Answer 1

you don't have to use external tools

$ a="/dir1/dir2/dir3/dir4"

$ echo ${a%/*}