Remove Column Header into the Output Text file

Add:

set underline off

to the beginning of the SQL script.

In my SQL scripts I have:

SET TERMOUT OFF
set colsep |
set pagesize 0 
set trimspool on
set pagesize  0 embedded on
SET heading on
SET UNDERLINE OFF
spool file_path
-- your SQL here
spool off

See this book for reference.

SQLPLUS COMMAND Skipped: set heading off

That message is most likely because you are not executing it through SQL*Plus, but some GUI based tool. You are using SQLPlus command in SQL Developer. Not all SQL*Plus commands are guaranteed to work with SQL Developer.

I would suggest you execute the script in SQLPlus and you would see no issues.

You need:

SET HEADING OFF

This will not include the column headers in the output.

Alternatively, you could also do this:

SET PAGESIZE 0

Using SQL Developer Version 3.2.20.10:

spool ON
spool D:\test.txt
SET heading OFF
SELECT ename FROM emp;
spool off

Spool file got created with no issues:

> set heading OFF
> SELECT ename FROM emp
SMITH      
ALLEN      
WARD       
JONES      
MARTIN     
BLAKE      
CLARK      
SCOTT      
KING       
TURNER     
ADAMS      
JAMES      
FORD       
MILLER     

 14 rows selected