Linux program to fetch IP address of host machine - study materials for competitive exams

/*Linux program to fetch IP address of host machine */

#include"stdio.h"
#include"stdlib.h"
#include"errno.h"
#include"netdb.h"
#include"sys/types.h"
#include"sys/socket.h"
#include"netinet/in.h"
#include"arpa/inet.h"

int main(int argc, char *argv[])
{
struct hostent *h;
if(argc != 2)
{
fprintf(stderr, "Usage: %s \n", argv[0]);
exit(1);
}
if((h=gethostbyname(argv[1]))==NULL)
{
herror("gethostbyname():");
exit(1);
}
else
printf("gethostbyname() is OK. \n");

printf("The host name is: %s \n", h->h_name);

printf("The IP address is: %s\n", inet_ntoa(*((struct in_addr *) h->h_addr)));

printf("The address length is: %d\n", h->h_length);

printf("Sniffing other names....sniff....sniff....sniff....\n");

int j = 0;
do
{
printf(" An alias #%d is: %s\n", j, h->h_aliases[j]);
j++;
}

while(h->h_aliases[j] != NULL);
printf("Sniffing other IPs....sniff....sniff....sniff....\n");

int i=0;
do
{
printf(" Address #%i is: %s\n", i, inet_ntoa(*((struct in_addr *) (h->h_addr_list[i] ))));
i++;
}

while(h->h_addr_list[i] != NULL);
return 0;
}