[gentoo-user] command line decipher

Can anybody explain me what I did. I run this command on my dd-wrt router (trying to clear the "traff" entries).
This command worked OK on my Linksys-router but my Asus-RT-N16 will not let me make a backup file. 
Now, when I try to make a backup, it doesn't prompt for file name, it just save the file with "0" bytes; yes the file is empty.

rw-r--r-- 1 fd users 0 Feb 11 09:09 nvrambak.bin

The command I run:

for i in `nvram show | grep traff- | cut -f1 -d=""`; do nvram unset $i; done

I think I will have to reload the dd-wrt firmware and restore old (good) nvrambak.bin

-- 
Thelma