Postgres 9.x: how to ascertain available disk space for work

I would like to gain a sense of how much available space the database has for temporary tables and scratch work. I do not have login access to t开发者_如何学Pythonhe machine where the database resides. Is there a mechanism via psql?

If you've access to an untrusted language, you can use it to issue shell commands as described in this blog post:

http://www.depesz.com/index.php/2007/08/12/hacking-with-postgresql/

In the post, he describes a step by step procedure to issue shell commands as user postgres on the server using an untrusted language.