babbu -12 Posting Whiz in Training

Hi,
I am trying to run sql command on unix.
this results in the following error
"sqlplus: not found"

Here is the unix part

sqlplus id/pass@some_server.com<<eof
 select sysdate from dual;
 exit
 eof

The database is on a remote server and.
Do I need to enter all the tns entries?