I had a large number of ebooks that looked like the following:
Walter%20Isaacson%20-%20Einstein_His%20Life%20And%20Universe.mobi
And because I’m lazy, I looked for an automated way to clean all of them up. This is how:
1. Back up all your files in another directory
2. Launch terminal
3. Go to the directory you’d like to perform the changes
4. Type: for i in *.mobi; do mv "$i" "`echo $i | sed ‘s/%20/ /g’`"; done
5. That’s it!