shell.cpp

#include <cstdlib>
#include <iostream>
#include <limits.h>
#include <string>
#include <unistd.h>
#include <vector>

int main() {
  while (true) {
    std::cout << ">";
    std::string s = "";
    std::getline(std::cin, s);

    std::vector<std::string> tokens;
    std::string token = "";
    for (char c : s) {
      if (c == ' ') {
        tokens.push_back(token);
        token = "";
      } else
        token += c;
    }
    if (!token.empty())
      tokens.push_back(token);

    if (tokens.empty())
      continue;

    std::cout << tokens[0] << " -> ";
    for (int i = 1; i < tokens.size(); i++)
      std::cout << tokens[i] << " ";
    std::cout << std::endl;

    if (tokens[0] == "exit")
      break;
    else if (tokens[0] == "cd") {
      if (tokens.size() == 2) {
        std::string path = tokens[1];
        if (!path.empty()) {
          chdir(path.c_str());
          std::cout << "cd invoked with " << tokens[1] << std::endl;
        }
      } else if (tokens.size() == 1) {
        const char *home = getenv("HOME");
        if (home != nullptr) {
          chdir(home);
          std::cout << "cd back to home\n";
        }
      }
    } else
      std::cout << "External command\n";
  }
  return 0;
}