void __procfdname(char* buf, unsigned fd) {
  unsigned i, j;
  for (i = 0; (buf[i] = "/proc/self/fd/"[i]); i++)
    ;
  if (!fd) {
    buf[i] = '0';
    buf[i + 1] = 0;
    return;
  }
  for (j = fd; j; j /= 10, i++)
    ;
  buf[i] = 0;
  for (; fd; fd /= 10)
    buf[--i] = '0' + fd % 10;
}