example of trigger to track DB changes - Mailing list pgsql-sql

I've looked through the trigger examples in the html doc and the src
tree but didn't find the one I was looking for.

I want to set up a trigger to track changes (add/update/delete) to rows
in two tables.  This can be through inserting OID's or acctname's
(acctname of web users) into a "changed_rows" table that keeps track of
changed rows.

Would someone provide some source code that does this?  I'm assuming a
lot of people have done this... I'm using 6.3.2 ...

thanks!
Michael