calling pl/sql function from unix shell script

I want to call a pl/sql function from a unix shell script and get the return value. This is how I use sql from within a script:

   SQL_STR="select sysdate from dual;"
   echo ${SQL_STR} | sql
   echo $?
How can I do the same thing but calling a pl/sql function and getting the returned value? Received on Tue Dec 11 2001 - 11:40:41 CST