Controlling a MX42HS via Bash

ser.sh

#!/bin/bash

# Validate input is present and is 1-4
[[ $1 && $1 != *[^1-4]* ]] || { echo "Invalid input." >&2; exit 1; }

# Free TTY from any process reading it
lsof -t /dev/ttyUSB0 | xargs -r kill -9

# Set output to File Descriptor 3
exec 3</dev/ttyUSB0

# Set TTY parameters (baud rate, etc)
stty -F /dev/ttyUSB0 57600 raw -echo

# Send command to switch all out to in[1-4]
echo "EZS OUT0 VS IN$1" > /dev/ttyUSB0

# Await a response from TTY
while [ "$response" = "" ]; do
    # Read from FD3 and echo to STDOUT
    read -e output <&3
    response=$(echo "$output")
    echo $output
done

# Release FD3
exec 3<&-
# Logging to STDOUT for review

echo "Expected OUT0 VS IN"$1
echo "Received" $output
if [[ "$output" == *"OUT0 VS IN$1"* ]]; then
	echo "Match!"
	exit 0
else
    echo "Did not match."
    exit 1
fi