Allow --write-out output to be written to a file

[ed0d2b2ce19451f2]

I would find it useful to have a way to cause the --write-out output of the curl tool to be written to a file instead of stdout or stderr which may both be in use for other purposes.

One way to achieve this might be new format variables such as file=<name> causing subsequent output to overwrite the file at <name> and file+=<name> causing subsequent output to be appended to the file at <name>.

Example use case:
curl --progress-meter --write-out '%{file=out.json}%{json}' --url 'https://example.com/large_file' | tee large_file | sha256sum > large_file.sha256

I suspect there's a workaround on Linux involving mkfifo, but I don't believe a similar CLI tool is available on Windows.

Thoughts?

[bagder]

I think this sounds like a great idea!

[bagder]

@ed0d2b2ce19451f2 Are you interested in implementing it?

[bagder]

See #11416

[rpluim]

Why would this need to handle all the mess involved in creating files?

curl --write-out=3

and then the usual tools can redirect/append that file descriptor any way you want.

[emanuele6]

This can be closed I think; curl 8.3.0 allows -w '%output{foo.json}%json'.

[timzhang926]

Thank you very much for saving my life.

[bagder]

Yeps, this is now implemented and shipped.