Bash读取退格按钮行为问题

这是一个简短的示例编程我正在使用它,如果有任何帮助：

#!/bin/bash

colour(){ #$1=text to colourise $2=colour id
        printf "%s%s%s" $(tput setaf $2) "$1" $(tput sgr0)
}
game_over() { #$1=message $2=score      
        printf "n%sn%sn" "$(colour "Game Over!" 1)" "$1"
        printf "Your score: %sn" "$(colour $2 3)"
        exit 0
}

score=0
clear
while true; do
        word=$(shuf -n1 /usr/share/dict/words) #random word from dictionary 
        word=${word,} #to lower case
        len=${#word}
        let "timeout=(3+$len)/2"
        printf "%s  (time %s): " "$(colour $word 2)" "$(colour $timeout 3)"
        read -t $timeout -n $len input #read input here
        if [ $? -ne 0 ]; then   
                game_over "You did not answer in time" $score
        elif [ "$input" != "$word" ]; then
                game_over "You did not type the word correctly" $score;
        fi  
        printf "n"
        let "score+=$timeout" 
done