How to check the original size of the log file before compression

Using curl command need to check the size of the log file pushed into elasticsearch .

Scenario : I am using index.codec: best_compression in yml file so using /_stats i see the compressed size of the log file i want to compare with the original size of the log file .....Using what command i can see that???

You will be after https://www.elastic.co/guide/en/elasticsearch/plugins/current/mapper-size.html