Interact with system command prompt

[billie]

Uhm... It seems that IPython got some problems:
http://ipython.scipy.org/doc/manual/node12.html

In details:

>Note that this does not make IPython a full-fledged system shell. In particular, it has >no job control, so if you type Ctrl-Z (under Unix), you'll suspend pysh itself, not the >process you just started.

>What the shell profile allows you to do is to use the convenient and powerful syntax of >Python to do quick scripting at the command line.