Client Tools :: Delimited Output From Sqlplus

I have a requirement to get a delimited output file by executing a select query.

For e.g.

select id, name, age from customers;

i need the output as,
id,name,age
123,devi,23
34,abi,20
4900,infy,23

i tried select id||','||name||','||age from customers;

but am getting the following output....

id||','||name||','||age
123,devi,23
34,abi,20
4900,infy,23

But i want to remove those pipes in between the column name.

I tried colsep also... but there am getting the output as.,

id,name,age
123, devi, 23
34, abi, 20
4900, infy, 23

some unwanted spaces in between...but i want the output as this...

id,name,age
123,devi,23
34,abi,20
4900,infy,23

the query which am using is stored in a .sql file.