在c或objective-c中交互式命令行应用程序的简单示例?

I'd like to write a simple interactive command line program in C or Objective-C. Something that prompts the user for input and then acts on that input, then prompts the user for more input. I've googled "interactive command line application" and several variations on that theme but am not coming up with any simple examples of what I'm looking for. I'd like to write a simple interactive command