[homebrewer]

This should work?

  curl --dump-header /dev/fd/xxx https://google.com

or

  mkfifo headers.out
  curl --dump-header headers.out https://google.com

unless I'm misunderstanding you.

[stabbles]

Ah yeah, `/dev/fd/xxx` works :) somehow thought that was Linux only.

[xantronix]

(Principal Skinner voice) Ah, it's a Bash expression!