title: how to change a single letter in filenames all over the file system?
body: <p>i have hundreds of files with special characters ('æ', 'ø' and 'å') in their filenames.</p>
  
  <p>i cannot copy these to my external mntfs disk without renaming.</p>
  
  <p>the files are in dozens of different folders. there are thousands of other files without these letters in there as well.</p>
  
  <p>i'd like to replace the special characters with their placeholders ('ae', 'oe' and 'aa'), while keeping the rest of the filename intact.</p>
  
  <p>i'm on ubuntu. i'm thinking of using grep, sed and tr, but i don't know exactly how.</p>