bin/59190: ftp(1): support server-controlled caching

[campbell+netbsd%mumble.net@localhost]

>Number:         59190
>Category:       bin
>Synopsis:       ftp(1): support server-controlled caching
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    bin-bug-people
>State:          open
>Class:          change-request
>Submitter-Id:   net
>Arrival-Date:   Mon Mar 17 15:35:00 +0000 2025
>Originator:     Taylor R Campbell
>Release:        current
>Organization:
The CacheFTP Expiration
>Environment:
>Description:
It would be nice if you could do something like

ftp -o cachedata -c cachemeta https://example.com/url

and ftp(1) would consult cachemeta and stop if it indicates a fresh result, or query https://example.com/url and save information from any cache-control or expires directives in cachemeta at the same time as it saves the data in cachedata for the next time you run the same command.

RFC 7234: Hypertext Transfer Protocol (HTTP/1.1): Caching
https://www.rfc-editor.org/rfc/rfc7234.html
>How-To-Repeat:
write a script that fetches a seldom-changing data file like https://data.iana.org/rdap/dns.json every time
>Fix:
Yes, please!