Linux网络编程：gethostbyname()的应用

主程序：gethostbyname.c

[cpp] view plaincopy

1. #include <netdb.h>  
2. #include <string.h>  
3. #include <stdio.h>  
4. int main(int argc, char *argv[])  
5. {  
6.     if (argc != 2)  
7.     {  
8.         printf("Usage:%s domain_name\n", argv[0]);  
9.         return 1;  
10.     }  
11.     struct hostent *ht = NULL;  
12.     // char host[20] = "www.google.com";  
13.     // ht = gethostbyname(host);  
14.     ht = gethostbyname(argv[1]);  
15.     if (ht)  
16.     {  
17.         int i = 0;  
18.         printf("Host:%s \n", argv[1]);  /* 原始域名 */  
19.         printf("Name:%s\n", ht->h_name);    /* 名称 */  
20.         /*协议族AF_INET为IPv4或者AF_INET6为IPv6 */  
21.         printf("Type:%s\n", ht->h_addrtype == AF_INET ? "AF_INET" : "AF_INET6");  
22.         /* IP地址的长度 */  
23.         printf("Legnth:%d\n", ht->h_length);  
24.         /* 打印IP地址 */  
25.         printf("\n");  
26.         printf("IP Address:\n");  
27.         for (i = 0;; i++)  
28.         {  
29.             if (ht->h_addr_list[i] != NULL)  
30.             {                   /* 不是IP地址数组的结尾 */  
31.                 printf("IP:%s\n", inet_ntoa((unsigned int *)ht->h_addr_list[i]));   /*打印IP地址 */  
32.             }  
33.             else  
34.             {                   /*达到结尾 */  
35.                 break;          /*退出for循环 */  
36.             }  
37.         }  
38.         /* 打印域名地址 */  
39.         printf("\n");  
40.         printf("Domain Name:\n");  
41.         for (i = 0;; i++)  
42.         {                       /*循环 */  
43.             if (ht->h_aliases[i] != NULL)  
44.             {                   /* 没有到达域名数组的结尾 */  
45.                 printf("alias %d:%s\n", i, ht->h_aliases[i]);   /* 打印域名 */  
46.             }  
47.             else  
48.             {                   /*结尾 */  
49.                 printf("\n");  
50.                 break;          /*退出循环 */  
51.             }  
52.         }  
53.     }  
54.     return 0;  
55. }  

makefile文件：

[cpp] view plaincopy

1. CC = gcc  
2. all:app  
3.       
4. app: gethostbyname.o  
5.     $(CC) gethostbyname.o -o app  
6.       
7. clean:  
8.     rm -f app *.o  

运行效果：

[root@ShiGuang gethostbyname]# make
gcc    -c -o gethostbyname.o gethostbyname.c
gcc gethostbyname.o -o app
[root@ShiGuang gethostbyname]# ls
app  gethostbyname.c  gethostbyname.o  Makefile
[root@ShiGuang gethostbyname]# ./app www.google.com.hk
Host:www.google.com.hk 
Name:www-hk.l.google.com
Type:AF_INET
Legnth:4

IP Address:
IP:72.17.67.8
IP:80.17.67.8
IP:88.17.67.8
IP:96.17.67.8
IP:104.17.67.8
IP:112.17.67.8

Domain Name:
alias 0:www.google.com.hk

[root@ShiGuang gethostbyname]#