如何打印hostent结构体中的所有数据

问题：

hostent是gethostbyname()和gethostbyaddr()都会涉及到的一个结构体。代码如下：

struct hostent {
  char  *h_name;
  char  **h_aliases;
  int   h_addrtype;
  int   h_length;
  char  **h_addr_list;
  };

gethostbyname()的原型是：

struct hostent *gethostbyname(const char *name);
函数的传入值是域名或者主机名，例如"www.google.com"、"191.168.1.253"等；
函数的返回值：

成功时，返回一个指向hostent结构的指针；

失败时，返回NULL。

编程调试过程中需要查看所取到的IP地址等信息，所以将hostent的全部内容打印出来就对调试很有帮助了。

解决办法：

#include <stdio.h>
#include <stdlib.h>
#include <netdb.h>
#include <sys/socket.h>

int main(int argc, char *argv[])
{
	char *ptr,**pptr;
	struct hostent *host;
	char str[32];
	char *hostname;

	if (argc < 2) {
		fprintf(stderr, "USAGE: ./pri-hostent Hostname(of ip addr such as 192.168.1.101)\n");
		exit(1);
	}

	/* get the host name */
	hostname = argv[1];

	// if ((host = (struct hostent*)gethostbyname(argv[1])) == NULL) {
	if ((host = (struct hostent*)gethostbyname(hostname)) == NULL) {
		perror("gethostbyname");
		return(1);
	}
	printf("Host name is: %s\n", host->h_name);
	/* printf all the aliases of host */
	for(pptr = host->h_aliases; *pptr != NULL; pptr++) {
		printf("  alias of host: %s\n",*pptr);
	}
	printf("Host addrtype is: %d\n", host->h_addrtype);
	printf("Host length is: %d\n", host->h_length);
	// // printf("Host is: %x\n", *((struct in_addr*)host->h_addr));
	/* printf ip address according to addrtype */
	switch(host->h_addrtype) {
		case AF_INET:
		case AF_INET6:
			pptr = host->h_addr_list;
			/* print all the aliases,inet_ntop() is called */
			for(; *pptr!=NULL; pptr++) {
				inet_ntop(host->h_addrtype, *pptr, str, sizeof(str));
				printf("  address: %s\n", str);
			}
		break;
		default:
			printf("unknown address type\n");
		break;
	}

	return 0;
}

程序的运行结果：

dingq@wd-u1110:~/hwsvn/2sw/1prj_linux/pdu/src/branches/pdu-isocket/isocket$ ./pri-hostent 
USAGE: ./pri-hostent Hostname(of ip addr such as 192.168.1.101)
dingq@wd-u1110:~/hwsvn/2sw/1prj_linux/pdu/src/branches/pdu-isocket/isocket$ ./pri-hostent www.google.com
Host name is: www.l.google.com
  alias of host: www.google.com
Host addrtype is: 2
Host length is: 4
  address: 74.125.128.106
  address: 74.125.128.147
  address: 74.125.128.99
  address: 74.125.128.103
  address: 74.125.128.104
  address: 74.125.128.105