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Comment by mdaniel | Hacker News Reader

I'm sure this solves someone's problem, but reading https://everything.curl.dev/cmdline/variables.html makes me wonder whether curl really needs this added complexity

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Folks using range requests will certainly welcome these as a great improvement. Without them, you need some ugly shell around your curl command to do it right, sending headers manually and slicing files in the shell.

And, if you don’t need them, don’t use them! Have you seen how many options curl has? But never good ones to support range requests until now.

I'm _pretty sure_ you're referring to `-C - -o $filename` and not this behavior. This one allows slurping ranges of local files and sending those in their entirety. I am open to maybe one day it does something crazypants with `-X PATCH --variable "fred@file[867-5309]"` or such but I doubt gravely that it does any such thing today

As shown here:

  $ python3 -m http.server 9090 &
  # that doesn't matter, just return _something_ on :9090
  $ ls -l .DS_Store
  -rw-r--r--@ 1 mdaniel  staff  18436 Dec 30 11:30 .DS_Store
  $ curl -vo .DS_Store -C - http://127.0.0.1:9090/.DS_Store
  ** Resuming transfer from byte position 18436
    % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                   Dload  Upload   Total   Spent    Left  Speed
    0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0*   Trying 127.0.0.1:9090...
  * Connected to 127.0.0.1 (127.0.0.1) port 9090
  > GET /.DS_Store HTTP/1.1
  > Host: 127.0.0.1:9090
  > Range: bytes=18436-
  > User-Agent: curl/8.7.1
  > Accept: */*

One can see where curl helpfully loaded the local file's 18436 size, set up the Range header, and included it on the first-contact with the http server.

While digging into this, there's actually one for its modification time, too. Curl knows all:

  $ curl -v --time-cond .DS_Store -o .DS_Store -C - http://127.0.0.1:9090/.DS_Store
  > If-Modified-Since: Mon, 30 Dec 2024 19:30:50 GMT

As for your "well, just don't use it then" stance, it has been my experience in building software that the Law of Unintended Consequences is brutal. The first bug report filed where someone discovers that a `--header` argument cannot contain {{ anymore due to a fat-fingered function change will let me put another quarter in the I Told You So jar

> Without them, you need some ugly shell around your curl command to do it right, sending headers manually and slicing files in the shell.

This seems much more readable than the stuff introduced here, and I would still heavily prefer to do it this way.

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