Modern scanners usually have several front panel buttons which are intended to
trigger certain actions like copying, faxing or mailing the scanned document.

This daemon queries the scanner button status several times per second. If it
detects that a button is pressed, it runs a shell script which the button
number is passed to as a command line argument. Because scanbuttond is
accessing the scanner directly via libusb, there should be no conflicts with
SANE or other scanner drivers: scanbuttond simply won't touch the scanner
hardware while you are using SANE. This means that you can still scan even when
running scanbuttond.

Authors:
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Bernhard Stiftner
Dirk Wriedt
J. Javier Maestro
Hans Verkuil
James Gilliland
Oliver Edelmann
Christian Bucher
David Froehlich
Milan Zamazal