pg_controldata [ datadir ]
pg_controldata prints information initialized during initdb, such as the catalog version and server locale. It also shows information about write-ahead logging and checkpoint processing. This information is cluster-wide, and not specific to any one database.
This utility may only be run by the user who initialized the cluster because it requires read access to the data directory. You can specify the data directory on the command line, or use the environment variable PGDATA.