if [ "$1"=="hellp" ];then
echo "Hello! How are you?"
elif [ "$1"=="" ];then
echo "You must input paramenters"
else
echo "The only accept parameter is hello"
fi
少了空格:
if [ "$1" == "hellp" ];then
echo "Hello! How are you?"
elif [ "$1" == "" ];then
echo "You must input paramenters"
else
echo "The only accept parameter is hello"
fi