Re: [RFE] Improve etag handling with --etag-compare-update

On 2025-04-28, Daniel Stenberg wrote:
>On Mon, 28 Apr 2025, Aleksei via curl-users wrote:
>
>>I'm trying to implement a "download only if updated on a remote
>>resource" functionality with a curl script using etags.
>>
>>Currently the etag file saved with --etag-save becomes useless after
>>a single update on a remote resource.
>
>I don't understand. Can you elaborate? If the remote resource is
>indeed updated, surely it should download again and update the etag
>file?
>
> / daniel.haxx.se || https://rock-solid.curl.dev

I'm asking for "and update the etag file" part to be done by curl.

Scenario:
1) curl downloads a webpage, saving etag file in file0.etag
2) website updates a webpage (update 1)
3) curl uses "--etag-compare file0.etag" and re-downloads the page -
    so far so good
4) website updates a webpage (update 2)
5) How do I check that webpage is updated now? "--etag-compare
    file0.etag" will re-download even if update 2 has been downloaded

Currently I would have to add a check at #3 to save the etag in a temp
file, compare to file0.etag and copy it over if necessary - a
script-side workaround I'm trying to avoid.
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