(spinner1)oracle@spinner[~]$ cat test.sh
#!/bin/bash

ORACLE_SID=spinner1
#ORACLE_HOME etc etc

FOO=`sqlplus -s /nolog <<EOF
connect / as sysdba
set pages 0
set feedback off
select 'cat dog foo' from dual;
EOF
`

echo SQLPLUS said: $FOO
(spinner1)oracle@spinner[~]$ ./test.sh
SQLPLUS said: cat dog foo
(spinner1)oracle@spinner[~]$