Script for SHOW SGA command

Can please you send me the SQL script that SQL*Plus actually runs for SHOW SGA command?
When you issue SHOW SGA in SQL*Plus, then it runs the following SQL statement for you:

SELECT name,value FROM v$sga;

However, the first line of output from SHOW SGA is the following SQL statement:

SELECT 'Total System Global Area',SUM(value) FROM v$sga;

Performing a UNION ALL ties it all together:

SELECT 'Total System Global Area',SUM(value) FROM v$sga
UNION ALL
SELECT name,value FROM v$sga;