Curl FHIR API Post Question

Folks, I need help understanding the purpose and expected values for a command line parameter
@RESOURCE_FILE used in the following curl post command.

curl -X POST
-H “Authorization: Bearer $(gcloud auth application-default print-access-token)”
-H “Content-Type: application/json; charset=utf-8”

But unable to understand what will appear in --data @RESOURCE_FILE variable

It carries the data that you want to pass to the HTTP body. The mentioned data is present in the file named RESOURCE_FILE accessible from where the curl command is fired.

Thanks Sachin. Very much appreciated. Could you please share your contact info. I may have some adhoc part time work if you are interested.