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

find . -regex ".*html$" | while read line;
 do 
    A=`basename ${line} | sed 's/html$/htm/g'`;
    B=`dirname ${line}`;
    mv ${line} "${B}/${A}";
 done