[root@localhost ~]# su - postgres
-bash-3.1$ psql postgres
Welcome to psql 8.1.11, the PostgreSQL interactive terminal.

Type:  \copyright for distribution terms
       \h for help with SQL commands
       \? for help with psql commands
       \g or terminate with semicolon to execute query
       \q to quit

postgres=# SHOW STATUS;
ERROR:  unrecognized configuration parameter "status"
postgres=#