#!/usr/bin/env bash

curl \
    -vv \
    --cookie cookies.txt \
    --cookie-jar cookies.txt \
    http://localhost/login \
    -d '{
        "email": "user@whatever.com", "password": "password"
    }'

If you are finding that the cookies.txt file is not being generated or is empty, then look at the output from curl.

We’re using verbose flags (-vv) so you should see something like this. 

* Added cookie some_cookie="Some+cookie" for domain localhost, path /, expire 0
< Set-Cookie: some_cookie=Some+cookie; path=/; domain=localhost; secure

If you see any errors or no cookies being sent, then the issue is probably that the server is not sending cookies properly.