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size_t read_tty(uint8_t *buff, size_t length){
    ssize_t L = 0;
    fd_set rfds;
    struct timeval tv;
    int retval;
    FD_ZERO(&rfds);
    FD_SET(comfd, &rfds);
    tv.tv_sec = 0; tv.tv_usec = 50000; // wait for 50ms
    retval = select(comfd + 1, &rfds, NULL, NULL, &tv);
    if (!retval) return 0;
    if(FD_ISSET(comfd, &rfds)){
        if((L = read(comfd, buff, length)) < 1) return 0;
    }
    return (size_t)L;
}