Commandline Defrag Only

Im looking to create a bat file, so that I can defrag my c drive fully and only defragment my external drives. I know there are command line options and also a shell extension to just defrag the fragmented files.

Thanks for any help!

What's the question?

How do I just defrag my external drive via the commandline, like defrag the fragmented files only. I THINK its the command im using below?

"C:\Program Files\Defraggler\df.exe" /S E:\