/*
 *  This program takes an IP address as the single command line argument
 *  and performs a reverse DNS lookup to determine the host name, if any. 
 *
 *  Eric Myers <myers@umich.edu>
 *  Deparment of Physics, University of Michigan, Ann Arbor
 *  @(#) $Id: hname.c,v 1.2 1999/08/02 21:25:05 myers Exp myers $
 */


#include <sys/types.h>
#include <stdio.h>		/*  NULL  */
#include <netinet/in.h>
#include <ctype.h>
#include <netdb.h>		
#include <arpa/inet.h>		/* in_addr */
#define AF_INET         2	/* internetwork: UDP, TCP, etc. */

/***#define INTERNIC    "internic.net" /*  */

#define INTERNIC    "whois.ripe.net" 

main(argc, argv)
     int argc;
     char *argv[];
{
  struct in_addr HostAddr;
  unsigned long haddr;
  struct hostent *host;
  char *HostName;
  
  /* Convert string argument to internet address */

  HostAddr.s_addr = inet_addr(argv[1]);

  /* Look up host name using IP address  */

  host = gethostbyaddr((char *)&HostAddr, sizeof(HostAddr), AF_INET);

  /* Print name if succesfull, otherwise just the address */

  if (host == NULL ) {
    HostName = inet_ntoa(HostAddr);
    printf("%s is unknown.\n", HostName); 
    printf("(Try `whois -h %s %s` or variations to find the owner.)\n", 
	    INTERNIC, HostName);
  }
  else {
    HostName = host->h_name;
    printf("%s\n", HostName);
  }
}