SQLite attach all databases in a directory

Hi I have an sqlite database called 'main.db' where I attach all the databases that are in the directory 'db' (e.g. 'db/db1.db' , 'db/db2.db' and so on).

I would like to know if there is a way to save 'main.db' so that the attachements are remembered across sessions.

Also when in 'main.db' how can I create a new database 'db/db3.db' and have it attached automatically when I open 'main.db'?

I usually use the sqlite3 shell for my databases maintenance.