C++17(C11): Bounds-checking getenv_s()

C++17 added the bounds-checking function getenv_s().

#include <cstdlib>
#include <iostream>
using namespace std;

int main()
{
  char   buffer[20];
  size_t environmentVariableValueStringLength;

  getenv_s(&environmentVariableValueStringLength, buffer,
           sizeof(buffer) - 1, "OS");

  cout << buffer << endl;
  return 0;
}
// Output: Windows_NT

Reference: http://en.cppreference.com/w/c/program/getenv