Can I receive data on the Arduino by sending data to /dev/ttyACM0? I'm working on a Raspberry Pi connected to an Arduino.
When I execute

echo 'Hello' &gt; /dev/ttyACM0


, the Arduino receives the data, as indicated by its LED. How can I read the data on the Arduino and process it?
Use Serial.read() there are plenty of examples that come with the Arduino IDE, just make sure the baud rates on the Raspberry Pi and Arduino match.