/*
   gethostbyname.c: illustrate the use of gethostbyname function.

	compile: cc -c gethostbyname.c -lnsl
*/

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

/* -----------------------------------------------------------------
   paddr: print the IP address in a standard decimal dotted format
   ----------------------------------------------------------------- */
void paddr(unsigned char *a)
{
   printf("%d.%d.%d.%d", a[0], a[1], a[2], a[3]);
}


int main()
{
   char hname[100];
   struct hostent *hp;		/* host pointer */
   char **p;			/* help variable to access h_aliases[ ] */
   int  **a;                    /* Help variable to access h_addr_list[ ] */

   int  addr;
   int  i;

   printf("Enter hostname: ");
   scanf("%s", hname);

   hp = gethostbyname(hname);

   if (hp == NULL)
    { printf("host information for %s not found\n", hname);
      exit(1);
    }

   printf("official hostname h_name = `%s'\n", hp->h_name);

   printf("Host has this alias list:\n");

   p = hp->h_aliases;                    // p[i] is a string (char *)
   for ( i = 0 ; p[i] != NULL; i++ )
   {
       printf("\tAlias %d: %s\n", i+1, p[i]);
   }

/* ----------------------------------------------
 *  This is how to use incrementing pointer....
 *
   for (p = hp->h_aliases; *p != 0; p++) 
   { 
       printf("\t%s\n", *p);
   }
*/

   printf("Host's address type = %d (should be AF_INET = %d)\n",
		hp->h_addrtype, AF_INET);
   printf("Host's address length = %d\n", hp->h_length);


   printf("List of Internet addresses for host:\n");

   a = (int **) hp->h_addr_list;
   for (i = 0; a[i] != 0; i++) 
   { 
      printf("\tIP address %d: ", i+1);
      paddr( (void*) a[i] );
      printf("\n");
   }
}