How can I kow my permissions?

I'm programming a database application that uses the API, but I have
some security issues that I have to manage, so I need to know my access
rights on a table and the "try" technique is not appropiate because if I
get a "Permission denied" then my transaction block is aborted and I
don't want that to happend.
The psql program can read it with the \z option so I know that it can be
done, so, how? from tha API, a query? which?.

Thanks in advance and sorry for my English, I speak Spanish.