bash - macOS - charge defaults to show/hide hidden files

#!/bin/bash

set -euo pipefail
IFS=$'\n\t'

if [[ $# -ne 0 ]]; then
ARG=$(echo "$1"|tr '[:upper:]' '[:lower:]')
if [[ "$ARG" =~ ^(no|off|disable|false|0)$ ]]; then STATE="NO";
   elif [[ "$ARG" =~ ^(yes|on|enable|true|1)$ ]]; then STATE="YES";
   else echo "error: invalid argument"; exit 1; fi
else
   STATE="YES"
fi
if [[ "$STATE" == "NO" ]]; then
   echo "info: not showing any hidden files";
elif [[ "$STATE" == "YES" ]]; then
   echo "info: showing all files"
else
   echo "error: unknown script state"
   exit 1
fi

( set -x;
  defaults write com.apple.finder AppleShowAllFiles $STATE 1> /dev/null
)