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

   int main(void)
   {
     int                sfd, i;
     struct ifreq       ifr;
     struct sockaddr_in *sin = (struct sockaddr_in *) &ifr.ifr_addr;

     memset(&ifr, 0, sizeof ifr);

     if (0 > (sfd = socket(AF_INET, SOCK_STREAM, 0))) {
       perror("socket()");
       exit(1);
     }

     strcpy(ifr.ifr_name, "eth0");
     sin->sin_family = AF_INET;

     if (0 == ioctl(sfd, SIOCGIFADDR, &ifr)) {
       printf("%s: %s\n", ifr.ifr_name, inet_ntoa(sin->sin_addr));
     }

     return 0;
   }