Use of shell scripts---while loop

While loop: Tests a condition repeatedly, as long as the condition is set up and executed repeatedly

The condition can be: test the expression, or the Boolean value true (the condition is always true) and false (the condition is always false)

vi useradd_while.sh # #将下面脚本改写为新建用户的脚本

#!/bin/bash

Pre=stu

I=0

While [$i-le 10];

Do

Useradd $PRE $i

echo 123123 |passwd--stdin $PRE $i

Userdel-r $PRE $i

i=$ (expr $i + 1)

Let i++

Done

: Wq

1. function random, let, exit:

Random is a function of generating a stochastic number

Echo $RANDOM # #生成随机数

Ehco $RANDOM% # #获取100内的随机数

echo $RANDOM% # #获取1000内的随机数

The Let command acts as a self-decrement operation for a variable:

I=1

Let i++

Echo $i

Let i++

Echo $i

Let i--

Echo $i

Expr $i + 1 #体会体会

Comprehensive application: Define a random value for true, you lose the right to stop and see how many times you can lose

VI banji.sh

#/bin/bash

p=$ (expr $RANDOM% 1000)

T=0

echo "Please insert a number like this (1-999)"

While True;do

Read-p "Please give number:" INT

Let t++

If [$INT-eq $P];then

echo "Your luckly. Right! "

Echo $T

Exit 0 # #当你输对了则退出程序脚本

elif [$INT-gt $P];then

echo "Too High"

Else

echo "Too Low"

Fi

Done

: Wq

2, distinguish Exit,break

Exit quit the program (script), break just exits the loop body

VI while.sh

#!/bin/bash

I=0

j=$ (expr $RANDOM% 10)

While True;do

Echo $i

Let i++

Sleep 1 # #休眠1秒避免死循环产生, can be removed try

If [$i-eq $j];then

echo "OK, $j random"

Break # #将break替换成exit看看效果

Fi

Done

Df-ht

: Wq

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Use of shell scripts---while loop