zwartrood

#!/usr/bin/env bash

# Change volume (disk) names here:
D1='T7Zwart'
D2='T7Rood'

# Mount point of external disks
M=/Volumes/

# Is the disk connected?
checkvol () {
	[ -e "$M$1" -a -d "$M$1" -a -r "$M$1" -a -w "$M$1" ] || {
		echo "Disk not found or not accessible: $1" >&2
		exit 1
	}
	return 0
}

checkvol "$D1"
checkvol "$D2"

# Is rsync available?
APP=rsync
BIN="$(which $APP)"
[ -z "$BIN" ] && { echo "Command not found: $APP" >&2; exit 2; }

# Disk free space on MacOS or Linux:
OS="$(uname)"
if [ "$OS" = 'Darwin' ]; then
	F1=$(df -g "$M$D1" | tail -n1 | awk '{print $4}')
	F2=$(df -g "$M$D2" | tail -n1 | awk '{print $4}')
elif [ "$OS" = 'Linux' ]; then
	F1=$(df -BG "$M$D1" | tail -n1 | awk '{print $4}' | grep -oP '\d+')
	F2=$(df -BG "$M$D2" | tail -n1 | awk '{print $4}' | grep -oP '\d+')
else
	echo "Unknown system: $OS" >&2
	exit 3
fi

# Show disk free space and offer to opt out:
echo 'Free space on disk:'
echo
printf "   %-15s %5u GB\n" "$D1" "$F1"
printf "   %-15s %5u GB\n" "$D2" "$F2"
echo
IFS=
read -p "Completely synchronise disks $D1 and $D2? (y/N) " -n 1 -s -r
echo

# Do the thing if confirmed
if [[ "$REPLY" =~ ^[Yy]$ ]]
then
	ARG='-auv --exclude=.Spotlight-V100 --exclude=.Trashes --exclude=.fseventsd --exclude=.DS_Store'
	echo
	echo "   Synchronising from $D1 to $D2 ..."
	echo
	$APP $ARG "$M$D1/" "$M$D2/"
	echo
	echo "   Synchronising from $D2 to $D1 ..."
	echo
	$APP $ARG "$M$D2/" "$M$D1/"
else
	exit 4
fi