Use oracle SET values in PL/SQL - oracle

Question

I was requested to set some environment parameters to migration files. However, such parameters as SQLBLANKLINES for instance, are only valid in sqlplus, other tools (e.g. Flyway) would be broken by its usage. Same is for autocommit.
Is there any way to perform following:
declare
v1 varchar2(60)
begin
v1 := SHOW SQLBLANKLINES
if (v1 is not empty) then
SET SQLBLANKLINES ON
end if;
end;
/
Or somehow query environment for available parameters to set?
Or somehow determine that exactly sqlplus is being used?
I'm aware of SHOW and SET commands, but I don't know how to place their results to variable and call SET inside PL/SQL.
Oracle is 11g.

Answer 1

You can't reference SQL*Plus commands in PL/SQL, as PL/SQL doesn't recognise them. Moreover, you can't use conditional statements directly in a SQL*Plus script, so you have to get a bit creative. You can, however, have a script that creates and runs another script, which you can use to inject conditional statements.
For example, this is a script that I use to either let my release script continue or not (it exits SQL*Plus):
continue_or_exit.sql:
prompt Do you want to continue script execution?
accept yn prompt 'Y / N : ';
set termout off;
set verify off;
set heading off;
set pause off;
set echo off;
column aaaa newline;
spool continue_or_exit_output.sql
select decode(upper('&&yn'), 'Y', 'prompt Executing ...',
'prompt Stopped'
),
decode(upper('&&yn'), 'Y', '', 'accept return_key prompt ''Press <Return>''') aaaa,
decode(upper('&&yn'), 'Y', '', 'exit') aaaa
from dual;
spool off;
set termout on;
#continue_or_exit_output.sql
set termout on;
set verify on;
set heading on;
You ought to be able to amend that for your case to decide whether to print out the relevant SQL*plus commands or not.

Answer 2

You cannot call SQL*Plus, or any client, commands from within PL/SQL. It is executed entirely on the server. You can tell which client is being used, at least if the client is well-behaved, but that doesn't really help you as you still can't use that information to control which client commands are issued.
The simplest approach may be to write a core script with the migration commands, and then a wrapper script for specific clients; so if you had core_migration.sql you could have another script called sqlplus_migration.sql that just did:
SET SQLBLANKLINES ON
-- any other SQL*Plus-specific set-up you want
SET PAGESIZE 0
SET LINESIZE 200
SET SERVEROUTPUT ON SIZE UNLIMITED
WHENEVER SQLERROR EXIT FAILURE
-- etc.
-- Run core migration script
#core_migration
exit 0;
SQL*Plus needs to be able to find the core script though, so it might be better/necessary to pass the full path to that with a substitution variable:
...
SET DEFINE ON
-- Run core migration script passed via command line
#&&1
exit 0;
... then call it as:
sqlplus -s -l usr/pwd #sqlplus_migration /path/to/core_migration.sql
(I don't like putting the credentials on the command line; your script could prompt for them instead but you suggested you wanted it to be non-interactive).
I'm not familiar with Flyway - it may just want to call the core script with no extra steps.