As of my Experience,I worked like below..
Passed parameter from command line to pig script filename and date..

pig  -f  myscript.pig --param file="india_" --param nw=$(date +"%Y-%m-%d-%s")  

In the pig script.

%declare FILE_PREFIX '$file$nw ';

A = load '/user/root/$FILE_PREFIX'   USING PigStorage(',') as (id1, name1);

dump A;