[Info-vax] FTP FYI

[David Jones]

On Monday, November 23, 2020 at 4:25:43 PM UTC-5, Steven Schweda wrote:
> > For really large savesets, is there something BACKUP can do but ZIP
> > can't? [...] 
> 
> Not specific to large files, but Info-ZIP programs generally don't 
> handle an alias or hard link. On VMS or elsewhere, I believe.

In the process of figuring out how to pull data out of a Excel .xlsx file, I studied the
zip format a lot (MS office files are a directory tree of XML modules saved in
zip format to save space). I don't think there is anything stopping the multiple
central directory entries from pointing to the same file data. If the file is created
is OS extensions (e.g. -V to save VMS attributes), link information will be saved.
I recently modified my web-based zip file browser to recognized the symbolic
organization and follow the link when extracting the data.

The format started in the MS-dos days and is still most comfortable in that
environment. The unix world still seems to favor a gzipped tar over zip.
One quirk is the binary timestamp format only has a 2 second resolution
 (another case where you can use extension data to get the original timestamp).

Zip format supports a large number of compression methods, but I rarely see
anything but the default 'deflate' compression method.