C++ :: Redirect Shell Standard Output Into Program Stream?

I want to take the standard output of a shell command (in Red Hat, using tcsh, in my case) and redirect it into my program for processing.

(Then ideally I would love to take the output of my program and redirect it to yet another command, but this is a second issue.) Simple example: I naively thought this might work:

I want to type this on the shell:

Code: $ echo Harry > hello and I was expecting this output on my terminal:
Code: $ hello, Harry And this would be my simple hello program:
Code: #include <iostream>
#include <string>
int main() {
std::string usrInput;
std::cin >> usrInput;
std::cout << "hello, " << usrInput << std::endl;
return 0;
}