Usb and arduino control

Hi. I have an idea for a project. But I need to know how to use arduino and a usb drive together. I need to arduino to read the usb and there will be a file on the usb and depending in what is contained in that file it will set a specific pin or pins to high.
Thanks Tim

Does the file need to be on USB or can it be on an SD card.

If it has to be a USB memory stick, you'd need to configure the Arduino as a USB host, using a Shield.

Also, what format is the "file" ie FAT, FAT32 etc etc as formats like NTFS are unlikely to be practical, I suspect it would need to be FAT, (if the USB host shield can read memory devices)

It has to be a usb. Fat32.

OK. Fat32 may be possible.

I'd take a look at the USB Shield stuff https://www.sparkfun.com/products/9947 and decide whether it looks like it will fly

And

Sparkfun mention thumb drives, but I don't see anything about it on the actual project page, or the github repo.

Ok. All that really says is that the usb mass storage device support will be coming in the future. Any other ideas?

Use a different board that has the appropriate USB host functionality.

E.g Raspberry PI

Or write the required USB host code for the arduino shield yourself.