Shell script for setting mouse sensitivity

mouse_sensitivity.sh

#!/bin/bash

flag=true

while [ "$flag" == true ]; do
  xinput --list
  echo "##################################################"
  echo "Select the ID of your input device:"

  read input_device

  selected_device=`xinput --list | grep id=$input_device`

  if [ -z "$selected_device" ]; then
    echo "Input device with id: \"$input_device\" not found."
    echo "Would you like to try again? [Y/N]"
    again_flag=true
    while [ "$again_flag" == true  ]; do
      read again_input
      if [ "$again_input" == "Y" ] || [ "$again_input" == "y" ]; then
        again_flag=false
      elif [ "$again_input" == "N" ] || [ "$again_input" == "n" ]; then
        echo "Bye!"
        exit 1
      else
        echo "I don't understand. Please enter [Y/N]"
      fi
    done
  else
    echo "Your selected device:"
    printf "\n"
    echo $selected_device
    printf "\n"
    input_flag=true
    while [ "$input_flag" == true ]; do
      echo "Would you like to change sensitivity of this device? [Y/N]"
      read confirm_input
      if [ "$confirm_input" == "Y" ] || [ "$confirm_input" == "y" ]; then
        flag=false
        input_flag=false
        break
      elif [ "$confirm_input" == "N" ] || [ "$confirm_input" == "n" ]; then
        echo "Select another device? [Y/N]"
        another_flag=true
        while [ $another_flag == "true" ]; do
          read another_select
          if [ "$another_select" == "Y" ] || [ "$another_select" == "y" ]; then
            another_flag=false
            input_flag=false
            break
          elif [ "$another_select" == "N" ] || [ "$another_select" == "n" ]; then
            echo "Bye!"
            exit 1
          else
            echo "I don't understand. Please enter [Y/N]"
          fi
        done
      fi
    done
  fi
done

current_value=`xinput --list-props 15 | grep "Device Accel Constant Decel" | cut -f3`
echo "Choose the deceleration value (current = $current_value). Higher is slower (default = 1)"
read decel_value
xinput --set-prop $input_device "Device Accel Constant Deceleration" $decel_value
echo "Done!"