Actions requiring commit

This may sound wierd for those not coming from an Oracle background, but
in Oracle land, certain actions such as writing to a native operating
system file,
placing a job on a queue for asynchronous processing, and such like
actions don't actually happen until commit time.

What's the postgres story? If I write to a native operating system file,
(and don't commit), does the output appear immediately (no counting internal
small delay) ?

What about issuing a "system" (shell) comnmand? Causing an signal,  (er
"Notify" in postrges land, I guess) , putting something on a queue via
PGQ or similar
tool?

Do all or any of those require a commit to "make it so" or not?