A couple of points first:

- The table names in the database and the script "t_fn.txt" are not the same. ("fn_test" and "test_a")
- "test_f" in the script "t_fn.txt" is only going to confuse sqlplus. What is it?

Regarding the main script:
Do you want to:
(a) execute "t_fn.txt" thereby inserting 1 record into table "fn_test" and then
(b) invoke function "test_fn" so that it fetches all 3 records (2 existing + 1 new)?

If you redirect the t_fn.txt script ("< t_fn.txt") to sqlplus, it will only run the script and disregard the commands inside the here-doc. You will have to execute the script within the here-doc.

Secondly, "l_refcursor" can be only be assigned the value of a compiled object. In this case, it is the function "test_fn". You cannot execute an external SQL script (anonymous PL/SQL block, "t_fn.txt" in this case) and assign it to "l_refcursor".

Considering all the points above, the following works in my system.

In Oracle:

Code:

SQL> 
SQL> create table fn_test (a number, b number, c number);

Table created.

SQL> insert into fn_test values(1,2,3);

1 row created.

SQL> insert into fn_test values(3,4,5);

1 row created.

SQL> commit;

Commit complete.

SQL> -- create function
SQL> create or replace function test_fn
  2  return sys_refcursor
  3  as
  4      p_ref_out sys_refcursor;
  5  begin
  6      open p_ref_out for select * from fn_test;
  7      return p_ref_out;
  8  end;
  9  /

Function created.

SQL> show errors
No errors.
SQL> 
SQL> --
SQL> select * from fn_test;

	 A	    B	       C
---------- ---------- ----------
	 1	    2	       3
	 3	    4	       5

2 rows selected.

SQL> 
SQL>

In Linux:

Code:

$ 
$ cat -n t_fn.txt
     1	insert into fn_test values(5555,4646,353454);
     2	commit;
$ 
$ 
$ cat -n main_script.ksh
     1	#!/bin/ksh
     2	sqlplus -s user/password@database << !
     3	set head off
     4	set echo off
     5	set define off
     6	set feedback off
     7	set serveroutput on
     8	set timing off
     9	set pages 0
    10	@t_fn.txt
    11	var l_refcursor refcursor
    12	exec :l_refcursor := test_fn
    13	print l_refcursor
    14	!
    15	
$ 
$ . main_script.ksh
      5555	 4646	  353454
	 1	    2	       3
	 3	    4	       5
$ 
$

The sqlplus variable "timing" is set to off by default, but in my setup it is set to on in the sqlplus profile script. So I set it off in the testcase above.
I set the variable "pages" to 0 in order to remove the extra blank line at the top where the header would have been.

I actually do not encounter the "PLS-00103" error. Try the above and see if it works in your system. Otherwise, more investigation will be required.