PostgreSQL Drop User Using Utility

dropuser removes an existing PostgreSQL user and the databases which that user owned. Only superusers (users with usesuper set in the pg_shadow table) can destroy PostgreSQL users.
Syntax:

dropuser [option...] [username]

Options Are:

Options	EXPLANATION
username	Specifies the name of the PostgreSQL user to be removed. You will be prompted for a name if none is specified on the command line.
-e --echo	Echo the commands that dropuser generates and sends to the server.
-i --interactive	Prompt for confirmation before actually removing the user.
-q --quiet	Do not display a response.
-h host --host host	Specifies the host name of the machine on which the server is running. If the value begins with a slash, it is used as the directory for the Unix domain socket.
-p port --port port	Specifies the TCP port or local Unix domain socket file extension on which the server is listening for connections.
-U username --username username	User name to connect as (not the user name to drop)
-W --password	Force password prompt (to connect to the server, not for the password of the user to be dropped).

db2=> \du            
                             List of roles
 Role name |                   Attributes                   | Member of 
-----------+------------------------------------------------+-----------
 gp1       | Cannot login                                   | {}
 nijam     |                                                | {}
 postgres  | Superuser, Create role, Create DB, Replication | {}
 rep       | Replication                                   +| {}
           | 1 connection                                   | 
 u3        | Password valid until 2017-06-06 00:00:00-04    | {}
 u6        |                                                | {}
 u8        | Superuser, Create role, Create DB              | {}
 u9        |                                                | {}

--Now give the super user password

-bash-3.2$ cd /opt/PostgreSQL/9.3/bin/
-bash-3.2$ ./dropuser u6
Password:    

--List the user u6 will be deleted

db2=> \du
                             List of roles
 Role name |                   Attributes                   | Member of 
-----------+------------------------------------------------+-----------
 gp1       | Cannot login                                   | {}
 nijam     |                                                | {}
 postgres  | Superuser, Create role, Create DB, Replication | {}
 rep       | Replication                                   +| {}
           | 1 connection                                   | 
 u3        | Password valid until 2017-06-06 00:00:00-04    | {}
 u8        | Superuser, Create role, Create DB              | {}
 u9        |                                                | {}

 --To remove user  u3 using the server on host p1, port 5432, with verification and a peek at the underlying command:

-bash-3.2$ ./dropuser -p 5432 -h p1 -i -e u3  -U postgres 
Role "u3" will be permanently removed.
Are you sure? (y/n) y
Password: 
DROP ROLE u3;

db2=> \du
                             List of roles
 Role name |                   Attributes                   | Member of 
-----------+------------------------------------------------+-----------
 gp1       | Cannot login                                   | {}
 nijam     |                                                | {}
 postgres  | Superuser, Create role, Create DB, Replication | {}
 rep       | Replication                                   +| {}
           | 1 connection                                   | 
 u8        | Superuser, Create role, Create DB              | {}
 u9        |