bash中的参数太多错误

/usr/local/bin/deleteall: line 6: [: too many arguments
/usr/local/bin/deleteall: line 11: [: too many arguments

这是我的代码：

#!/bin/bash
#Deletes all files in the current directory

read -p "You are about to delete all files in $(pwd). Are you sure you want to do this? y/n" yn
echo $yn
if [ [ "$yn" = "y" ] -o [ "$yn" = "Y" ] ] ; then
        for i in `ls`; do
                rm $i
        done
        exit;
elif [ [ "$yn" = "n" ] -o [ "$yn" = "N" ] ] ; then
        exit;
else
        read -p "Please enter y (yes) or n (no)"
        exit;
fi

这是整个输出：

You are about to delete all files in <my dir>. Are you sure you want to do this? y/nn
n
/usr/local/bin/deleteall: line 6: [: too many arguments
/usr/local/bin/deleteall: line 11: [: too many arguments
Please enter y (yes) or n (no)n

我究竟做错了什么？