How to use Operating System Commands while using define in sqlplus

Question

How to use Operating System Commands while using define in sqlplus . The Host OS is Linux
define report_name=PROD_${host date "+%b"}.html
The above is not working.
The output should be 
define report_name=PROD_JAN.html
Regards,
DB

Answer 1

of course I was talking nonsense: the problem here is the mixing of bind variables and DEFINE variables.
With the following changes the script should work (the conditions for begin_interval_time are perhaps not what you want):
variable snap1 number
variable snap2 number
variable rptname varchar2(20)
begin
SELECT min(snap_id) into :snap1 FROM dba_hist_snapshot WHERE CAST(begin_interval_time AS DATE) >= SYSDATE-1;
SELECT max(snap_id) into :snap2 FROM dba_hist_snapshot WHERE CAST(begin_interval_time AS DATE) >= SYSDATE-1;
end;
col file_name_value new_value report_name noprint
select 'PROD_'|| to_char(sysdate,'MON') || '_' ||  to_char(sysdate,'DD') file_name_value  from dual;
define  report_type  = 'html'
define num_days=2
define begin_snap=:snap1
define end_snap=:snap2
@@?/rdbms/admin/awrrpt.sql