[C] Getting a MAC address in C

void get_mac_addr( char* mac)
{
int fd;
struct ifreq ifr;

fd = socket(AF_INET, SOCK_DGRAM, 0);

ifr.ifr_addr.sa_family = AF_INET;
strncpy(ifr.ifr_name, "eth0", IFNAMSIZ-1);

ioctl(fd, SIOCGIFHWADDR, &ifr);

close(fd);

/* display result */
sprintf(mac, "%.2x:%.2x:%.2x:%.2x:%.2x:%.2x",
(unsigned char)ifr.ifr_hwaddr.sa_data[0],
(unsigned char)ifr.ifr_hwaddr.sa_data[1],
(unsigned char)ifr.ifr_hwaddr.sa_data[2],
(unsigned char)ifr.ifr_hwaddr.sa_data[3],
(unsigned char)ifr.ifr_hwaddr.sa_data[4],
(unsigned char)ifr.ifr_hwaddr.sa_data[5]);

}

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