I had a need to read such things as the backend locale and the catalog
version number from the current database, and couldn't find any existing
program to do that.

The attached utility produces this output:

linda:~$ pg_controldata
Log file id:                          0
Log file segment:                     5
Last modified:                        Wed Feb  7 19:35:47 2001
Database block size:                  8192
Blocks per segment of large relation: 131072
Catalog version number:               200101061
LC_COLLATE:                           en_GB
LC_CTYPE:                             en_GB
Log archive directory:                

--
Oliver Elphick                 <olly@lfix.co.uk>