使用gethostbyname时候遇到的莫名其妙的输出

[fzyz_sb]

直接上代码（代码摘自unp卷1第十一章）：

#include "myunp.h"

int main( int argc, char **argv )
{
	char	*ptr, **pptr;
	char	str[ INET_ADDRSTRLEN ];
	struct	hostent	*hptr;
	
	while ( --argc > 0 ){
		ptr = *++argv;
		if ( ( hptr = gethostbyname( ptr ) ) == NULL ){
			printf("gethostbyname error for host:%s:%s\n", ptr, hstrerror( h_errno ) );
			continue;
		}
		printf("official hostname:%s\n", hptr->h_name );
		for ( pptr = hptr->h_aliases; *pptr != NULL; pptr++ )
			printf("\talias:%s\n", *pptr );
		switch( hptr->h_addrtype ){
			case AF_INET:
				pptr = hptr->h_addr_list;
				for ( ; *pptr != NULL; pptr++ )
					printf("\taddress:%s\n", *pptr );
//					printf("\taddress:%s\n", inet_ntop( hptr->h_addrtype, *pptr, str, sizeof(str)));
			break;
			default:
				printf("unknown address type");
				break;
		}
	}

	exit(0);
}

而程序输出：

root@ThinkPad-T430i:/home/leichaojian# ./hostent www.baidu.com
official hostname:www.baidu.com
	address:（这里是乱码字符，CSDN不允许显示）a!kwww.（这里是乱码字符，CSDN不允许显示）a!lu.com
	address:（这里是乱码字符，CSDN不允许显示）a!lu.com

所以，使用inet_ntop函数（我已经注释掉了）的时候，直接报异常错误了。这到底是为什么呢？

[小笨和漂向北方]

h_addr_list is really an array of struct in_add in disguise... So, in order to access this array that appears to be char**, you should do:

addr_list = (struct in_addr **)he->h_addr_list;
 for(i = 0; addr_list[i] != NULL; i++) {
        printf("%s ", inet_ntoa(*addr_list[i]));
    }

As gethostbyname man page indicates, it points to the network addresses for the host (in network byte order)

[fzyz_sb]

引用 1 楼 micropentium6 的回复:

h_addr_list is really an array of struct in_add in disguise... So, in order to access this array that appears to be char**, you should do:

addr_list = (struct in_addr **)he->h_addr_list;
 for(i = 0; addr_list[i] != NULL; i++) {
        printf("%s ", inet_ntoa(*addr_list[i]));
    }

As gethostbyname man page indicates, it points to the network addresses for the host (in network byte order)

你说的很正确。但是不知道为什么我的ubuntu系统上就是报错。我甚至找了网上的代码运行也是出错，搞不懂为什么，书上的代码应该也是正确的，你说的也是正确的，我也大概理解了。不过谢谢你，希望有一天我的编程能达到你的高度。