#include <stdio.h>  #include <sys/socket.h>  #include <sys/ioctl.h>  #include <netinet/in.h>  #include <net/if.h>  #include <string.h>  #include <arpa/inet.h>    int main(int argc, char **argv)  {      int sockfd;      struct ifreq ifr;        char *ifname="eth0";      strncpy(ifr.ifr_name, ifname, IFNAMSIZ-1);        sockfd = socket(AF_INET, SOCK_STREAM, 0);      if(ioctl(sockfd, SIOCGIFADDR, &ifr) == -1)      {          printf("Error\n");          return;      }        struct sockaddr_in *myaddr;      myaddr = (struct sockaddr_in*)&(ifr.ifr_addr);      printf("IP: %s\n", inet_ntoa(myaddr->sin_addr));  }