To have all the typical unix tools on the iPhone one usually installs BSD Subsystem. Unfortunatly if one installs this, it is impossible to remove it. Only a complete restore will do that.
Another have been released, Cydia, that claims to have a much better solution and follows much better the unix standard. (The BSD Subsystem has been hacked together quickly just to have something to work with on iPhone).
You can read more about this on the page where you can get Cydia:
hawkin 