"Gevik babakhani" <gevik@xs4all.nl> writes:
> Does anyone know how to execute an OS command from pgsql. I would like to
> create a trigger that op on firing would run/execute an external program.
Use any of the "untrusted" PLs to execute system() or the like.
Whether this is a good idea or not is a different question --- there are
excellent reasons why it is a *bad* idea to execute outside-the-database
actions from within a trigger. Mainly that the actions won't be undone
if the transaction later rolls back, and now your database state is
inconsistent with outside-the-database state. See the list archives for
many past discussions of this point and safer ways to design your
application.
(BTW, this is hardly material for -hackers.)
regards, tom lane