Renaming Files

#!/bin/bash
for file in foo[0-9]*.png; do
  # strip the prefix ("foo") off the file name
  postfile=${file#foo}
  # strip the postfix (".png") off the file name
  number=${postfile%.png}
  # subtract 1 from the resulting number
  i=$((number-1))
  # copy to a new name in a new folder
  cp ${file} ../newframes/$(printf foo%08d.png $i)
done

http://stackoverflow.com/questions/55754/how-to-zero-pad-numbers-in-file-names-wit-a-bash-script