a simple trigger?

hello,

i have created a trigger that executes a c function, foo(), after something
is inserted into my table. foo() is supposed to simply write a string to
some file. but after i do an INSERT, nothing is written.
i compiled the source file:
gcc -fPIC -g -c a.c
and then made a shared library:
gcc -shared -W1 -soname,mylib1.so.1 -o mylib1.so.1.0.1 a.o -lc
then i created the function before i created my trigger.
so what am i doing wrong?

i also tried creating a raw psql function (CREATE FUNCTION...) for my
trigger to call, but when i tried creating the trigger, it complained: the
function has to return an opaque type. but sql functions can't return type
opaque. what do i do?

i would appreciate any help anyone could give me.

thanks,
nguyen
da79c(at)hotmail(dot)com