prompt.cpp

#include <iostream>
#include <string>

std::string eval(std::string input)
{
  return std::string("\"") + input + std::string("\"");
}

const std::string PROMPT = "> ";

int main()
{
  std::cout << PROMPT;
  std::string input;
  while (std::getline(std::cin, input)) {
    std::cout << eval(input) << "\n" << PROMPT;
  }

  std::cout << '\n';
}

prompt.log

$ ./prompt
> time machine
"time machine"
>