lab1.c

通过输入IP地址或域名获得其相关信息比如别名等

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

int main(int argc,char *argv[])
{
char **pptr;
char str[32];

struct hostent *hptr;
struct in_addr hipaddr;

int n;

n=inet_aton(argv[1],&hipaddr);
printf("%d %s",n,argv[1]);

if(n==0)
{
	if((hptr=gethostbyname(argv[1]))==NULL)
	printf("gethostbuname error for host: %s\n",argv[1]);


	printf("offical hostname: %s\n",hptr->h_name);
	for(pptr=hptr->h_aliases;*pptr!=NULL;pptr++)
	printf("alias:%s\n",*pptr);
switch(hptr->h_addrtype)
{
case AF_INET:
case AF_INET6:
pptr=hptr->h_addr_list;
for(;*pptr!=NULL;pptr++)

printf("address:%s\n",inet_ntop(hptr->h_addrtype,*pptr,str,sizeof(str)));
break;

}
}

if(n==1)
{


	if((hptr=gethostbyaddr((char *)&hipaddr,4,AF_INET))==NULL)
	{
		printf("error\n");
		return 1;
	}
	printf("offical hostname:%s\n",hptr->h_name);
	for(pptr=hptr->h_aliases;*pptr!=NULL;pptr++)
	printf("alias: %s\n",*pptr);

	switch(hptr->h_addrtype)
	{
		case AF_INET:
		case AF_INET6:
		pptr=hptr->h_addr_list;
		for(;*pptr!=NULL;pptr++)
		printf("address:%s\n",inet_ntoa((struct in_addr)(hipaddr)));
		break;
                                                                                
}
}
exit(0);
}