/* This certifies an integer is in a format that atoi() can recognize. */
static int verify_atoi(const char* s)
{
  int rv = 0;
  int i = 0;
  int len = strlen(s);
  /* Allow optional number of spaces */
  for( ; i < len ; ++i ) {
    if( !isspace((int)s[i]) ) {
      break;
    }
  }
  /* Allow optional minus sign */
  if( s[i] == '-' ) {
    ++i;
  }
  /* Allow consecutive digits */
  for( ; i < len ; ++i ) {
    if( isdigit((int)s[i]) ) {
      rv = 1;
    } else {
      break;
    }
  }
  /* Allow optional number of spaces */
  for( ; i < len ; ++i ) {
    if( !isspace((int)s[i]) ) {
      rv = 0;
      break;
    }
  }
  return rv;
}