C源碼:通過IP地址查找主機名 findip.c
 

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第八軍團 時間：2004-1-23 15:47:06 
   
/* 
 * This program is free software; you can redistribute it and/or modify 
 * it under the terms of the GNU General Public License as published by 
 * the Free Software Foundation; either version 2 of the License, or 
 * (at your option) any later version. 
 * 
 * This program is distributed in the hope that it will be useful, 
 * but WITHOUT ANY WARRANTY; without even the implied warranty of 
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
 * GNU General Public License for more details. 
 * 
 * You should have received a copy of the GNU General Public License 
 * along with this program; if not, write to the Free Software 
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 
 * 
 * 
 * Filename: findip.c 
 * Created : Nov. 10th 1995 @ 4:30pm 
 * Author  : SrfRoG (srfrog@itek.net) 
 * Descrip.: This cute little program will attempt to resolve 
 *   an IP address to its hostname. Then prints the results 
 *   to standard output. 
 * --------------------------------------------------------------------- 
 * To compile this program: 
 * Linux: gcc -O2 -m486 -s -o findip findip.c 
 * AIX, BSD: gcc -O2 -s -o findip findip.c 
 * SunOS: gcc -O2 -lnsl -s -o findip findip.c 
 * Other: cc -o findip findip.c 
 */ 

#include <stdio.h> 
#include <sys/types.h> 
#include <sys/socket.h> 
#include <netinet/in.h> 
#include <arpa/inet.h> 
#include <netdb.h> 

int main(argc, argv) 
int argc; 
char **argv; 
{   
struct hostent *ip; 
unsigned long hostname; 

if (argc != 2) 
{ 
printf("Need to specify an IP address.\n"); 
exit(1); 
}  
if ((hostname = inet_addr(argv[1])) == -1) 
{ 
printf("Could not find %s\n", argv[1]); 
exit(1); 
} 
if ((ip = gethostbyaddr((char *)&hostname, sizeof(long), AF_INET)) != NULL) 
printf("%s is %s\n", argv[1], ip->h_name); 
else 
printf("Could not resolve %s\n", argv[1]); 
return 0; 
}