Curl Command: how do you register an account non-temporarily with Curl command?

I created a website that you can just create an account and login with that account, and then I tried to register an account by POST method and get the user information by GET method with Curl in terminal. But, it seemed that I can only get the user info while running the program. It means that the user I registered with Curl POST disappears from the database after shutting down the program. Is it possible to register an account that remains in the database non-temporarily?

This is the Curl command I used:

curl -X POST -H "Content-Type: application/json" -d /some contents/ http:///some address/

Best regards,