谁有更好的方法帮我实现下面的代码要完成的目标

read -p "username " A

grep "^\<$A\>" /etc/passwd

B=`echo $?`

if [$B -eq 0] ;then

grep "^\<$A\>" /etc/passwd |cut -d: -f7

else

echo "your input is wrong"

fi

read -p "n or N for next"  C

D=`echo "$C" | tr 'a-z' 'A-Z'

while ["$D" == " N" ];do

read -p "username " A

grep "^\<$A\>" /etc/passwd

B=`echo $?`

if [ $B -eq 0 ];then

grep "^\<$A\>" /etc/passwd | cut -d: -f7

else

echo "your input is wrong"

fi

read -p "n or N for next " C

D=`echo "$C" | tr 'a-z' 'A-Z'

done