Linux环境下通过c代码获取本机IP

#include <stdio.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/ioctl.h>
#include <linux/if.h>

long getlocalhostip ()
{
    int MAXINTERFACES = 16;
    long ip;
    int fd, intrface, retn = 0;
    struct ifreq buf[MAXINTERFACES];
    struct ifconf ifc;
    ip = -1;
    if ((fd = socket (AF_INET, SOCK_DGRAM, 0)) >= 0) {
        ifc.ifc_len = sizeof buf;
        ifc.ifc_buf = (caddr_t) buf;
        if (!ioctl (fd, SIOCGIFCONF, (char *) &ifc)) {
            intrface = ifc.ifc_len / sizeof (struct ifreq);
            while (intrface-- > 0) {
                if (!(ioctl (fd, SIOCGIFADDR, (char *) &buf[intrface]))) {
                    ip = inet_addr (inet_ntoa (((struct sockaddr_in *) (&buf[intrface].ifr_addr))->sin_addr));
                    break;
                }
            }
        }
        close (fd);
    }
    return ip;
}

union ipu
{
    long ip;
    unsigned char ipchar[4];
};

int main (int argc, char **argv)
{
    union ipu localip;
    localip.ip = getlocalhostip ();
    printf ("local ip:%x :%u.%u.%u.%u \n", localip.ip, localip.ipchar[0], localip.ipchar[1], localip.ipchar[2], localip.ipchar[3]);
    return 0;
}