Code:
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <net/if.h>
#include <arpa/inet.h>

#include <unistd.h>
#include <stdio.h>
#define MAX_IFS 64

int main()
{
    struct ifreq *ifr, *ifend;
    struct ifreq ifreq;
    struct ifconf ifc;
    struct ifreq ifs[MAX_IFS];
    int SockFD;


    SockFD = socket(AF_INET, SOCK_DGRAM, 0);


    ifc.ifc_len = sizeof(ifs);
    ifc.ifc_req = ifs;
    if (ioctl(SockFD, SIOCGIFCONF, &ifc) < 0)
    {
        printf("ioctl(SIOCGIFCONF): %m\n");
        return 0;
    }


    ifend = ifs + (ifc.ifc_len / sizeof(struct ifreq));
    for (ifr = ifc.ifc_req; ifr < ifend; ifr++)
    {
        if (ifr->ifr_addr.sa_family == AF_INET)
        {
            strncpy(ifreq.ifr_name, ifr->ifr_name,sizeof(ifreq.ifr_name));
            if (ioctl (SockFD, SIOCGIFHWADDR, &ifreq) < 0)
            {
              printf("SIOCGIFHWADDR(%s): %m\n", ifreq.ifr_name);
              return 0;
            }

printf("Ip Address %s\n", inet_ntoa( ( (struct sockaddr_in *)  &ifr->ifr_addr)->sin_addr)); 
      printf("Device %s -> Ethernet %02x:%02x:%02x:%02x:%02x:%02x\n", ifreq.ifr_name,
      (int) ((unsigned char *) &ifreq.ifr_hwaddr.sa_data)[0],
      (int) ((unsigned char *) &ifreq.ifr_hwaddr.sa_data)[1],
      (int) ((unsigned char *) &ifreq.ifr_hwaddr.sa_data)[2],
      (int) ((unsigned char *) &ifreq.ifr_hwaddr.sa_data)[3],
      (int) ((unsigned char *) &ifreq.ifr_hwaddr.sa_data)[4],
      (int) ((unsigned char *) &ifreq.ifr_hwaddr.sa_data)[5]);
 }
    }

    return 0;
}
see man page netdevice(7)