This is a command line directory utility that works on both Windows and Linux. It scans the directory information and store in a file. This allows two computers to be scanned at a different time and even in two different country and allows the comparison to be carried out at a different time and place. This allows terabytes of disk with millions of files and directories to be compared.  A sub feature is the capability to report the size of every sub-directory trees in the scan. It becomes useful when you want to clean up 2 TB external hard drive and want to know which sub-directory trees is the biggest so you can start tackling those first