bash script to convert a string from hex to decimal

hex.sh

HEX=c9fc17d693b58ad31448d1177728964591ad1c720b545a05c700395c980a7029
i=1
while (( i <= ${#HEX} ))
do
    char=$(expr substr "$HEX" $i 2)
    # echo "<$char>"
    printf "%d\n" 0x$char
    (( i += 2 ))
done