[simonblack]

Sorry. Unless I'm missing something completely, I have to ask: 'Why would you bother to reinvent the wheel?'

If you want something like bash, just use bash. If you want a CLI in a GUI environment, just use 'terminal', or'xterm' or similar.

If you're talking about apps that run in a CLI, then the world is your oyster. Use whatever you need depending on what the app requires.

If you're talking about what language to use, then just use which ever language that you're comfortable with that can/will produce a text output.