int
Select(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
       struct timeval *timeout)
{
        int             n;

        if ( (n = select(nfds, readfds, writefds, exceptfds, timeout)) < 0)
                err_sys("select error");
        return(n);              /* can return 0 on timeout */
}