$ nano evalconcat.txt
$ cat evalconcat.txt
$ hdfs dfs-put evalconcat.txt /pigexample
$ pig
grunt> A = LOAD '/pigexample/evalconcat.txt' USING PigStorage(',') AS (a1:chararray,a2:chararray,a3:int);
grunt> DUMP A;
Result = FOREACH A GENERATE CONcat (a1,'_',a2); DUMP Result;