Pad numerical values in filename with three digit value using sed

Question

I am passing a filename into my bash script and cleaning the name using sed. A few sample files would be:

Test 01.txt
Test v2 01.txt

I would

Answer 1

This might work for you (GNU sed):

sed  -r 's/[0-9]+/$(printf "%03d" &)/g;s/.*/echo "&"/e' file
Test 001.txt
Test v002 001.txt