The Cmd class provides a simple framework for writing
line-oriented command interpreters. These are often useful for
test harnesses, administrative tools, and prototypes that will
later be wrapped in a more sophisticated interface.
A Cmd instance or subclass instance is a line-oriented
interpreter framework. There is no good reason to instantiate
Cmd itself; rather, it's useful as a superclass of an
interpreter class you define yourself in order to inherit
Cmd's methods and encapsulate action methods.
The optional argument completekey is the readline name
of a completion key; it defaults to Tab. If completekey is
not None and readline is available, command completion
is done automatically.
The optional arguments stdin and stdout specify the
input and output file objects that the Cmd instance or subclass
instance will use for input and output. If not specified, they
will default to sys.stdin and sys.stdout.
Changed in version 2.3:
The stdin and stdout parameters were added.