#include "kernel/types.h"
#include "user/user.h"

int main(int argc, char *argv[]) {
  if (argc != 1) {
    // 错误输出到stderr（文件描述符2）
    fprintf(2, "Usage: uptime\n");
    exit(1);
  }

  fprintf(1,"up: %d\n",uptime());
  
  exit(0);
}