timing in PostgreSQL

Hi, i need you help Postgres gurus...

I have been modified postgres for a while... and i need to test the
performance (for now, only time) of my modifications against the original
postgres....

My first approach was to use the function clock() of the time.h C library,
in the postgres.c file.... but reading the file, i noticed that
you can set a group of options that print statistics (generals or specifics
to postgres modules, in the stdin) for each query that you send to postgres
Server...
So, i did it...

Now, i don't have a clue how interpreter what postgres print.... i search in
the postgres manual but i find nothing about it....

Now, where i can find information about how to read this statistics??? (this
sound a pg_admin question but read the second one)

And, those times are exclusive postgres times, or they include the expended
time of postgres in process the query, plus the time that postgres waits
when there are other process running in the SO (you kwon, multi tasking)???

By the way, is this a good approach, or i will have to take the first
approach that i mentioned???

Thanks.

Waiting your answers,
Carlos Chacon.