（转载）http://blog.sina.com.cn/s/blog_4065d7370100075l.html
具体代码如下：
#include <stdio.h>
#include <stdlib.h>
#include <sys pes.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>
#include <unistd.h>
#include <net/route.h>
#include <string.h>
int get_my_address (struct in_addr *addr)
{
struct ifreq req;
int sock;
sock = socket(AF_INET, SOCK_DGRAM, 0);
strncpy (req.ifr_name, "eth0", IFNAMSIZ);
if ( ioctl(sock, SIOCGIFADDR, &req) < 0 )
{
printf("failed to ioctl: %s\n", strerror (errno));
return 0;
}
memcpy (addr, &((struct sockaddr_in *) &req.ifr_addr)->sin_addr, sizeof (struct in_addr));
return 1;
}
int main(int argc, char *argv[])
{
struct in_addr addr;
char ip[32];
if(get_my_address(&addr))
{
//strncpy(ip, inet_ntoa(addr), sizeof(struct in_addr));
printf("IP Address : %s\n",inet_ntoa(addr));
}
return 0;
}