Re: Naming ETag files?

On 15-Jan-23 13:04, Paul Gilmartin via curl-users wrote:
> On 1/15/23 05:19:32, Timothe Litt via curl-users wrote:
>>     ...
>> If the filesystem supports extended attributes, an even better place 
>> would be to store the etag there, since in that case, moving, 
>> copying, renaming would automagically ensure that the etag is carried 
>> along. Linux xattr, Mac forks, NTFS 'streams', etc..
>
> Interesting.  The Mac and Linux xattr commands have a useful compatible
> overlap. So I could download with:
>     --etag-save tempfile.ETag
> tnen:
>     xattr -w user.aETag "$( cat tempfile.ETag )" downloaded-resource
>
> ... and reverse the process for --etag-compare for the next conditional
> download.
>
[and delete the tempfile.  And for mult-file downloads, handle each file.]

So: Yes, but it would be much better for curl to do it automagically.  
Users shouldn't have to work hard or be expert on the underlying 
technologies to have a good experience.  I'm all for flexibility for 
experts, but the defaults ought to provide the best performance for as 
many cases as possible.  That's why in an ideal world, I'd prefer to 
obsolete the --etag-save and --etag-compare switches and have curl do 
the right things. (dotfiles, extended attributes.)  Plus curl could hide 
the details of xattrs mac vs. linux vs solaris vs windows vs vms vs 
freebsd vs aix vs... And which filesystems support xattrs - it's not 
just per-os.  Falling back to a dotfile would keep things consistent.

   --no-etag would then let the experts experiment with options and test.

Progress isn't best measured in how many options can be added to express 
intent; rather, how few need to be specified to get the best results.  
The options should be reserved for exceptions when the best default 
action needs to b changed (as in testing), or cases where curl doesn't 
have the information necessary to make the best choice.

This doesn't just apply to curl, though its explosion of options is a 
pretty good example of how adding options with each feature can lose 
sight of making the user experience simple.


Timothe Litt
ACM Distinguished Engineer
--------------------------
This communication may not represent the ACM or my employer's views,
if any, on the matters discussed.

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