c语言获取本地ip

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <netinet/in.h>
#include <net/if.h>
#include <net/if_arp.h>
#include <arpa/inet.h>
#include <errno.h>
#define ETH_NAME        "eth0"        
int main() 
{         
 int sock;
 struct sockaddr_in sin;         
 struct ifreq ifr;
 sock = socket(AF_INET, SOCK_DGRAM, 0);
 if (sock == -1){
  perror("socket");
  return -1;
 }
 strncpy(ifr.ifr_name, ETH_NAME, IFNAMSIZ);
 ifr.ifr_name[IFNAMSIZ - 1] = 0;
 if (ioctl(sock, SIOCGIFADDR, &ifr) < 0){
  perror("ioctl");
  return -1;
 }
 memcpy(&sin, &ifr.ifr_addr, sizeof(sin));
 fprintf(stdout, "%s\n", inet_ntoa(sin.sin_addr));

 return 0;
}