shell脚本基本语法学习

#! /bin/sh
＃while 语句
echo "enter passwd"
read passwd
while [ $passwd != "aaa" ];do
echo "sorry try again"
read passwd
done

＃for 语句
#! /bin/bash
for i in a b c; do
echo "$i\n"
done

#case 语句

#! /bin/sh

echo "Enter a number"
read number
case $number in
1)
echo "you number is 1"
;;
2)
echo "yo number is 2"
;;
*)
exit 1
;;
esac

#if else elif fi

#! /bin/sh

echo "Is it morning? Please answer yes or no."
read YES_OR_NO
if [ "$YES_OR_NO" = "yes" ]; then
echo "Good morning!"
elif [ "$YES_OR_NO" = "no" ]; then
echo "Good afternoon!"
else
echo "Sorry, $YES_OR_NO not recognized. Enter yes or no."
exit 1
fi
exit 0