linux时间方面的设置

例如以下一段代码能够借鉴：

static void _sleep_response_timeout(modbus_t *ctx)
{
#ifdef _WIN32
    /* usleep doesn't exist on Windows */
    Sleep((ctx->response_timeout.tv_sec * 1000) +
          (ctx->response_timeout.tv_usec / 1000));
#else
    /* usleep source code */
    struct timespec request, remaining;
    request.tv_sec = ctx->response_timeout.tv_sec;
    request.tv_nsec = ((long int)ctx->response_timeout.tv_usec % 1000000)
        * 1000;
    while (nanosleep(&request, &remaining) == -1 && errno == EINTR)
        request = remaining;
#endif
}