how to execute same SQL script in all Oracle databases in Linux server [single shot]

Linux shell script: sample

[orcl@qact /home/oracle/adt]$ more all_db.sh 

#!/bin/bash

for I in GTD1 PTD1 FTD1 CTD1 MTD1 MSD1 # List of DB names
do

  echo "~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~"

  echo "executing scripts...."

  export ORACLE_SID=$I

  echo "DB Name: "$ORACLE_SID

  sqlplus -S -L  / as sysdba < /home/oracle/adt/adt.sql

  echo "Done."

done

[orcl@qact /home/oracle/adt]$ more adt.sql 

spool /home/oracle/adt/DB_result_$ORACLE_SID.log
set line 280
select name, open_mode, log_mode from v$database;
.
.
.
spool off;
exit;

[orcl@qact /home/oracle/adt]$ ./all_db.sh

[orcl@qact /home/oracle/adt]$ ll

total 8308

-rwxr--r-- 1 oracle dba    2567 Nov 15 12:38 adt.sql

-rwxr--r-- 1 oracle dba     314 Nov 15 12:02 all_db.sh

-rw-r--r-- 1 oracle dba   96709 Nov 15 12:39 DB_result_GTD1.log

-rw-r--r-- 1 oracle dba   90588 Nov 15 12:39 DB_result_PTD1.log

-rw-r--r-- 1 oracle dba   64756 Nov 15 12:39 DB_result_FTD1.log

-rw-r--r-- 1 oracle dba   92605 Nov 15 12:39 DB_result_CTD1.log

-rw-r--r-- 1 oracle dba   92408 Nov 15 12:39 DB_result_MTD1.log

-rw-r--r-- 1 oracle dba   92408 Nov 15 12:39 DB_result_MSD1.log

Note: " sqlplus -S -L " 

-S silent.
-L try login only once. (else 3 times)