To execute pig script from grunt shell you can use exec or run command. While the time of using the run command, all the commands present in the script file will be available in the grunt history, which is not the case with the exec command.
You can load the data file in PigStorage by using the following piece of code:-
product = LOAD 'hdfs://localhost:9000/product_dir/products.csv' USING PigStorage(',') as (product_id:int, product_name:chararray, price:int);
After loading the data files the next thing you can do is execute the script file, which is stored in HDFS by using the following commands:-