linux下c++如何输入不回显

#include <stdio.h>
#include <termios.h>
#include <unistd.h>
#include <iostream>
using namespace std;

int main(void){
    char c;
    static struct termios oldt, newt;
    tcgetattr( STDIN_FILENO, &oldt);
    newt = oldt;
    newt.c_lflag &= ~(ICANON);
    tcsetattr( STDIN_FILENO, TCSANOW, &newt);
    system("stty -echo");
    while((c=getchar())!= 'e') {
      char d = c + 'A' - 'a';
      cout << d << endl;
    }     

    system("stty echo");
    tcsetattr( STDIN_FILENO, TCSANOW, &oldt);
    return 0;
}

其中system("stty -echo") 与 system("stty echo") 之间的代码的执行都不会回显