Unix Environment variable for connect string in SQL*Plus

Question

I am using some environment variables to connect to a sql*plus session in unix.
they are exported as part of a file which contains the following and gets executed through the .profile.
export db_username=xxx
export db_password=xxx
export db_name=xxx
i have created a file abc.sql which contains the following
connect $db_username/$db_password@$db_name
Now, I have a shell script which uses this file inside it to connect to a sql*plus session and execute some queries.
The contents of the shell script :
API_CONNECT_SQL=abc.sql
sqlplus /nolog << THEEND
WHENEVER SQLERROR EXIT SQL.SQLCODE ROLLBACK
WHENEVER OSERROR EXIT FAILURE ROLLBACK
set timing on
@${API_CONNECT_SQL}
---- do something
EXIT
THEEND
Now, the sql*plus session is able to get db_username and db_password, but not the db_name. It says "TNS service name not found".
If I hardcode some database name in place of db_name, it connects properly.
Please let me know the problem and solution as well.
Any help appreciated.
thanks,
Vijay

Answer 1

for me this one works
# =========================================
# begin of script
# =========================================
export db_username=alpha
export db_password=bravo
export db_name=charly
echo "connect $db_username/$db_password@$db_name" > xxx.sql
API_CONNECT_SQL=/cfs/dummy1/0/appl/dummy2/rev_04/zzz/tst/xxx.sql
cat ${API_CONNECT_SQL}
sqlplus /nolog << THEEND
spool xxx
WHENEVER SQLERROR EXIT SQL.SQLCODE ROLLBACK
WHENEVER OSERROR EXIT FAILURE ROLLBACK
set echo on
host cat ${API_CONNECT_SQL}
@${API_CONNECT_SQL}
select * from dual;
spool off
EXIT
THEEND
# =========================================
# end of script
# =========================================