script for linux tablet setup on multiple monitors

#!/bin/bash
# setup active screen for tablet usage in a multi-monitor environment
# author: christopher barry
# license: public domain

##### C O N F I G U R A T I O N #####

# Configure left,right,center to match your xrandr display names
# to find them, run 'xrandr --query' to see the names of your ports.
declare -r left="DVI-1"
declare -r center="DisplayPort-0"
declare -r right="DVI-0"

# tablet name as expressed in /var/log/Xorg.0.log
# For Huion H610, it is: "HUION PenTablet"
declare -r tablet="HUION PenTablet"

##### E N D  C O N F I G U R A T I O N #####

##### S C R I P T  B E G I N S #####

function evar() {
    [[ ${#} -gt 0 ]] || return
    eval "echo -n \${$@}"
}

case "${1}" in

    left|center|right)

        # assign the graphics port from parameter
        screen=$(evar "${1}")
        [[ ${screen} ]] || {
            echo "oops! '${1}' has no graphics port value assigned."
            echo "did you configure the top section of this script ("$0") to match your setup?"
            exit 1
        }

        # verify we have tools to operate
        [[ $(which xrandr) ]] || {
            echo "You need xrandr installed for this script to function"
            exit 1
        }

        # verify configured port exists
        xrandr | grep -w connected | awk '{print $1}' | grep -qw "${screen}" || {
            echo "oops! cannot find graphics port ${screen} supposedly located @ ${1}"
            echo "did you configure the top section of this script ("$0") to match your setup?"
            exit 1
        }

        # get all instances of tablet
        declare -a ids=( $(grep  "${tablet}" /var/log/Xorg.0.log | grep "type:" | tr [[:punct:]] ' ' | awk '{ print $NF }' | sort -u) )

        for id in "${ids[@]}"; do

            # map each instance to the selected monitor
            xinput map-to-output ${id} "${screen}" &>/dev/null || {
                echo "an error occurred attempting to map ${tablet} id=${id} to ${1} screen '${screen}'"
                exit 1
            }
            echo -n "."

        done

        echo -e "\n${tablet} is now mapped to ${screen} located on ${1} monitor"
        exit 0
        ;;

    *)
        echo "Usage: $(basename "$0") <left|center|right>"
        exit 1
        ;;
esac