test-file

#!/bin/bash

#test code
#build list, with Quit at end

declare -a list
readarray -t list < <(apt-cache madison nvidia-driver |awk '{print $3}' |grep -v deb |grep -v mx)
list[${#list[@]}]="Disable Nvidia Developer Repo (default)"
list[${#list[@]}]="Quit"



#size of array
echo "size of array is " "${#list[@]}"

for i in ${!list[@]}; do
  echo "$i - ${list[$i]}"
done

#user enters a number of the driver they want
echo "choose a version"

read -e x

#validate string


case $x in
  *[!0-9]*) echo "Invalid Choice, try again" 
  #choose_version
  ;;
  *) if [ -z "$x" ]; then
	   echo "Keep Existing Selection"
     else if [ $x -gt $((${#list[@]}-1)) ]; then
		echo "Invalid Choice, try again"
	      else
		  VERSION=${list[$x]}
		  echo "version is " $VERSION
	     fi
    fi ;;
esac