compare the size of files with the same filename in two directorys

compare.sh

#!/bin/bash
DIR1=~/bar/
DIR2=~/foo/

SIZE1=0
SIZE2=0

for file in $DIR1*; do
        file2=$DIR2$(basename "$file")
        if [[ -f $file ]] && [[ -f $file2 ]]; then
                ((S1=$(stat -c%s "$file")))
                ((S2=$(stat -c%s "$file2")))
                echo $(basename "$file") size 1 $(($S1/1024/1024)) MB size 2 $((S2/1024/1024)) MB
                ((SIZE1+=$S1))
                ((SIZE2+=$S2))
        fi
done
echo "size of files in" $DIR1: $((SIZE1/1024/1024/1024)) GB
echo "size of files in" $DIR2: $((SIZE2/1024/1024/1024)) GB