第五节shell脚本中的运行流程控制(3.2)

2, 判断循环

a)whlie 语句

使用 while 循环结构, 当条件满足时反复执行指定动作, 否则终止

语法:

while 条件
do
	动作1
	动作2
	...
done

示例

1, 猜商品价格, 通过变量 RANDOM 获取随机数价格, 提示用户猜测并记录次数, 猜中后退出循环

vim price.sh
#!/bin/bash
PRICE=$[ $RANDOM % 100 ]
TIMES=0
while true
do
	read -p "please enter the product price [0-99] : " INT let TIMES++"
	if [ $INT -eq $PRICE ]
	then
		echo "Good luck,you guessed it."
		echo "You have guessed $TIMES times."
		exit 0
	elif [ $INT -gt $PRICE ]
	then
		echo "$INT is too high"
	else
		echo "$INT is too low"
	fi
done

2, 在文件中记录了用户名的名称, 请根据文件记录的用户名建立用户

vim userlist
user1
user2
user3

sh demo_while.sh userlist
#!/bin/bash
[ -z "$1" ] && { exit }
exec < $1
while read USERNAME
do
	useradd -r $USERNAEM && ehco $USERNAEME is created
done

3, 将之前用 for 语句创建的 test01-test30 用户删除

vim del_user.sh
#!/bin/bash
i=1
while [ $i -le 30 ]
do
	if [ $i -le 9 ]
	then
		user=test0$i
	else
		user=test$i
	fi
	
	if id -u $user $>/dev/null
	then
		userdel -r $user
	else
		echo "$user is not exists..."
	fi
	let i++
done