gethostbynameドメイン名に基づいてipアドレスを取得

gethostbyname関数はドメイン名に基づいてサーバのipアドレスを解析し、構造体struct hostentを返します.
struct hostent構造体

#include 

struct hostent {
	char * h_name; 		/ *       * /
	char ** h_aliases; 	/ *     ,           * /
	int h_addrtype; 	/ *      :IPV4-AF_INET* /
	int h_length; 		/ *        ，  IPv4    ， 32 * /
	char ** h_addr_list; / *    * /
}
#define h_addr h_addr_list [0] / *      * /

例:

//test_gethostbyname.c
#include 
#include 
#include 
#include 
#include 
#include 


int main(int argc, char **argv)
{
	char *hostname,**pptr;
	struct hostent *hptr;
	char str[32] = {0};


	hostname = argc < 2 ? "www.baidu.com" : argv[1];
	printf("hostname:%s
", hostname);


	if((hptr = gethostbyname(hostname)) == NULL)
	{
		printf("gethostbyname(%s) error(%s)
", hostname, strerror(errno));
		return 0;
	}

	printf("official hostname:%s
", hptr->h_name);   	//     

	for(pptr = hptr->h_aliases; *pptr != NULL; pptr++)	//         
		printf("alias: %s
", *pptr);

	switch(hptr->h_addrtype)  //      ，       
	{
		case AF_INET:
		case AF_INET6:
			pptr = hptr->h_addr_list;
				
			//           
			printf("first address: %s
", inet_ntop(hptr->h_addrtype, hptr->h_addr, str, sizeof(str)));
		
			for(; *pptr != NULL; pptr++)   //            
			{
				//inet_ntop:                      
				printf("address: %s
", inet_ntop(hptr->h_addrtype, *pptr, str, sizeof(str))); 
			}
			break;
		default:
			printf("unkown address type
");
			break;
	}
	return 0;
}

参考資料https://blog.csdn.net/wynter_/article/details/52529685 https://kenby.iteye.com/blog/1149534 https://blog.csdn.net/test1280/article/details/82949596