There are caveats, of course:
- NTFS supports transparent compression of files. There is the "actual" file size, and the "compressed" size. Which does -s return?
- NTFS supports sparse files. If a large section of a file contains NULL, the filesystem can save space by not allocating room for the NULL data. Here, I would assume -s would return the full size, not the "on disk" size.
- NTFS supports "alternate streams". A file can have many alternate streams, taking up data that I assume would never be reported by -s.
- Depending on the file size & cluster size, most files probably take up more space "on disk" than the contents of the file would suggest. Which does -s report here?
This is probably not an exhaustive list, I'm sure I'm forggeting something.
Edited by Chady -- closed ul tag.