Question

我是c编程的初学者，我想使用的是地址列表 hostent结构，但我无法计算有多少地址我的代码是

int main (int argc,  char *argv[])
{
  int i;
  struct hostent  *host_info;
  struct in_addr *address;
  if(argc <2)
    {
      printf("USAGE: %s <hostname>\n",argv[0]);
      exit(1);
    }
  host_info=gethostbyname(argv[1]);
  if(host_info==NULL)
    {
      printf("couldn't lookup %s\n",argv[1]);

    }
  else
    {
      for(i=0;i<??????????;i++){
      address=(struct in_addr *)(host_info ->h_addr_list[i]);
      printf("%s  has address %s\n",argv[1],inet_ntoa(*address));
      }
    }

}

Answer 1

host_addr结构不包含地址列表的长度。相反，地址列表中的最后一个条目是0（NULL）。所以循环host_info->h_addr_list[i] != 0

Answer 2

你可以这样做，

 while(host_info ->h_addr_list[i]  != NULL){
  address=(struct in_addr *)(host_info ->h_addr_list[i]);
  printf("%s  has address %s\n",argv[1],inet_ntoa(*address));
  }

如何计算**指针的索引

2 个答案: