getting IP addresses of network interfaces on Linux box

There are IOCTL's you can call on a socket fd, something like this, from
the top of my head:

  int fd;
  strict ifreq ifr;
  struct sockaddr_sin *sa;
  
  fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_IP);
  strcpy(ifr.ifr_name, ifname); /* Don't use strcpy */
  ioctl(fd, SIOGCIFADDR, &ifr);
  sa = (struct sockaddr_in *)(ifr.ifr_addr);