curl post json

curl -X POST -H "Content-Type: application/json" \
 -d '{"username":"abc","password":"abc"}' \
 https://api.example.com/v2/login

curl -d '{"key1":"value1", "key2":"value2"}' -H "Content-Type: application/json" -X POST http://localhost:3000/data

curl --data "param1=value1&param2=value2" https://example.com/post

curl -X POST -H "Content-Type: text/plain" --data "this is raw data" http://78.41.xx.xx:7778/