Enter password width asterisk (*) on the fly

enter_password.sh

#!/usr/bin/env sh

$USER="anonymous"

echo
unset password
prompt="Please input the $USER's Password: "
while IFS= read -p "$prompt" -r -s -n 1 char
do
    if [[ $char == $'\0' ]] ; then
        break
    fi
    # backspace
    if [[ $char == $'\177' ]] ; then
        prompt=$'\b \b'
        password="${password%?}"
    fi
    prompt='*'
    password+="$char"
done
echo
echo "Your password is: $password"