Add file extension to files with bash

Question

What is the good way to add file extension \".jpg\" to extension-less files with bash?

Answer 1

In my case i was not aware of the filetype so i used the mv command with the help of the file command to examine and possibly find the file type. This solution might not be perfect for all files since the file command might not recognize the filetype but it worked mostly good for me.

for f in *; do ext=$(file $f | awk '{print $2;}'); mv -n "$f" "$f.$ext"; done

The use of awk is to strip the second word of the string returned from the command file that is actually the extension.