Followup, second try. First of all, I'd like to apologize to the list for my previous message, I borked some finger gymnastics when switching tabs and sent and incomplete one. My fault. Sorry.
Now what I tried to say was: I did not spot it at first, looking at http://www.gzip.org/zlib/rfc-gzip.html#file-format I see: ISIZE (Input SIZE) This contains the size of the original (uncompressed) input data modulo 2^32. And given gzip -l is usually much faster than -tv I suspect it's just reporting this size. Francisco Olarte.