Sending e-mail from a trigger

I haven't paid much attention to the discussions of SPI, but I
remember seeing questions about the server-side system tasks in the
trigger context, among which sending mail was the most frequent.

I am not aware whether such questions were sufficiently answered in
the lists, so when I had to write my first ever trigger yesterday, I
felt like I was on my own with the system tasks (although the triggers
and plpgsql are explained very well in the docs). So, here's my take on e-mail:

http://wit.mcs.anl.gov/~selkovjr/pg_extensions/contrib.tgz

(see the README in mail/)

I believe it should be trivial to do other tasks in a similar way,
using sockets and rsh. At least, it is better to do it that way than
fork the backend.

--Gene