We want to monitor total size of database

Hello.

We want to monitor the following items with respect to PostgreSQL.
*Total Size of database
*Size of used space of the entire database
*Size of free space of the entire database
*Size of fragmentation area of the entire database

But the following items are getting monitored in PostgreSQL7.3.8.
("Pgstattuple" is used for monitoring)
*Total of sizes of all the tables in database
*Total of used space by all the tables in database
*Total of free space of all the tables in database
*Total of fragmentation area of all the tables in database

In short, in 7.3.8 we are not able to acquire the information on the space
related to
index but the information of the partial area of the database is monitored.

Therefore, we are in search of the method to monitor the space of the entire
database.

Our question is:
Is there any method available in PostgreSQL8.1.0 for monitoring the space of
the entire database ?

Best Regards,