Re: diff on .gz and .bz2 files

    Maybe the gzip algorithm uses some randomness in its compression?

No.  There's a timestamp in the gzip format (so a file can have its
mtime restored when it is gunzipped).

    > Of course, I could. But I think this may not be an efficient way if the
    > .gz file is too large, say of the order of GB.

The suggestion was to use fifos (named pipes).  Thus the uncompressed
versions do not actually exist on disk.