A file is a FIFO, if you read it from front to back and append data to the back. However, you should look at the Queue as a way of doing a FIFO. Why are you using a file as the FIFO? Are you sharing the data between two applications? You say that you can't do what you want with the options in LabVIEW; but which approaches have you tried? Show us some examples of your code, where you are getting stuck.