Postgres DB Size Command

Question

What is the command to find the size of all the databases?

I am able to find the size of a specific database by using following command:

select pg_database_size('databaseName'); 

Answer 1

You can enter the following psql meta-command to get some details about a specified database, including its size:

\l+ <database_name> 

And to get sizes of all databases (that you can connect to):

\l+ 

Answer 2

You can get the names of all the databases that you can connect to from the "pg_datbase" system table. Just apply the function to the names, as below.

select t1.datname AS db_name,          pg_size_pretty(pg_database_size(t1.datname)) as db_size from pg_database t1 order by pg_database_size(t1.datname) desc; 

If you intend the output to be consumed by a machine instead of a human, you can cut the pg_size_pretty() function.