How do I rename files in sub directories?

Question

Is there any way of batch renaming files in sub directories?

For example:

Rename *.html to *.htm in a folder which has directories

Answer 1

I'm sure there's a more elegant way, but here's the first thing that popped in my head:

for f in $(find . -type f -name '*.html'); do 
    mv $f $(echo "$f" | sed 's/html$/htm/')
done