shell编程——单双多分支条件语句(16)

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# if[条件判断式]；then
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# 程序
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# fi
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# 或者
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# if[条件判断式]
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# then
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# 程序
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# fi

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#!/bin/bash
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test=$(env | grep "USER" | cut -d "=" -f 2)
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if("$test"=="root")
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then
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echo "root"
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fi

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#!/bin/bash
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test=$(df -h | grep sda5 | awk '{printf $5}') | cut -d "%" -f 1)
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if["$test" -ge "90"]
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then
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echo "full"
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fi

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# if[条件判断式]
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# then
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# 条件成立时，执行的程序
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# else
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# 条件不成立时，执行的另一个程序
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# fi

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#!/bin/bash
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read -t 30 -p "please input a dir:" dir
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if[-d "$dir"]
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then
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echo "It's a dir"
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else
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echo "No"
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fi

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#脚本名不能写成httpd ，不然grep 无论Apache启动都能扫描到 httpd
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ps aux | grep httpd | grep -v grep
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#!/bin/bash
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test=$(ps aux | grep httpd | grep -v grep)
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if[-n "$test"]
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then
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echo "httpd is ok"
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else
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echo "httpd is no"
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/etc/rc.d/init.d/httpd start
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fi

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# if[条件判断式1]
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# then
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# 当条件判断1成立时，执行程序1
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# elif[条件判断式2]
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# then
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# 当条件判断式2成立时，执行程序2
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# .....
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# else
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# 当所有条件都不成立时，最后执行此程序
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# fi

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#!/bin/bash
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read -t 30 -p "Please input num1:" num1
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read -t 30 -p "Please input num1:" num2
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read -t 30 -p "Please input a operate:" ope
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if[-n "$num1" - a -n "$num2" -a -n "$ope"]
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then
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test1=$(echo $num1 | sed 's/[0-9]//g')
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test2=$(echo $num2 | sed 's/[0-9]//g')
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if[-z "test1" -a -z "$test2"]
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then
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if["$ope"='+']
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then
22 collapsed lines
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sum=$(($num1+num2))
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elif["$ope"='-']
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then
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sum=$(($num1-num2))
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elif["$ope"='*']
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then
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sum=$(($num1*num2))
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elif["$ope"='/']
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then
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sum=$(($num1/num2))
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else
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echo  "Please input a vaild symbol"
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exit 10
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fi
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else
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echo "Please input a vaild value"
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exit 11
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fi
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echo "请输入内容："
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exit12
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echo "$num1 $ope $num2 = $sum"

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#!/bin/bash
2

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read -p "Please input a filename:" file
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if[-z "$file"]
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then
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echo "Error, please input a filename"
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exit 1
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     elif[!-e "$file"]
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          then
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               echo "Your input is not a file !"
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               exit2
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     elif[-f "$file"]
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          then
11 collapsed lines
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               echo "Your input is not a file !"
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               exit 2
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     elif[-f "$file"]
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          then
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               echo "$file is a regulare  file !"
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     elif[-d "$file"]
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          then
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               echo "$file is a directory!"
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     else
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          echo "$file is an other file!"
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fi

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# case $变量名 in
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# "值1")
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# 执行程序1
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#  ;;
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# "值2")
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# 执行程序2
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#  ;;
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# ......
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# *)
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# 如果变量的值都不是一上的值，执行此程序
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# ;;
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# esac

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#!/bin/bash
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read -p "Please choose yes/no :" -t 30 cho
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case $cho in
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"yes")
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echo "your choose is yes!"
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;;
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"no")
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echo "your choose is no!"
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;;
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*)
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echo "your choose is error!"
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;;
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esac

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# 语法1：
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# for 变量 in 值1 值2 值3
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# do
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# 程序
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# done

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#!/bin/bash
2

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cd /root/test
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ls *.tar.gz > ls.log
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for i in $(cat ls.log)
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do
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tar -zxf $i &> /dev/null
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done
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rm -rf /lamp//ls.log
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语法2：
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for ((初始值;循环控制条件;变量变化))
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do
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程序
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done

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#!/bin/bash
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#从1加到100
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s=0
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for ((i=1;i<=100;i=i+1))
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do
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s=$(($s+$i))
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done
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echo "The sum of 1+2+3...+100 is :$s"

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#!/bin/bash
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#批量添加指定数量的用户
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read -p "Please input user name:" -t 30 name
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read -p "Please input number of user:" -t 30 num
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read -p "Please input passwd of user:" -t 30 passwd
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if[!-z "$name" -a ! -z "$num" -a ! -z "$passwd"]
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then
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y=$(echo $num | sec 's/[0-9]//g')
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if[-z "$y"]
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then
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for((i=1;i<=$num;i=i+1))
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do
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/usr/sbin/useradd $name$i &>echo $passwd | /usr/bin/passwd --
3 collapsed lines
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done
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fi
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fi

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#!/bin/bash
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#删除用户
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for i in $(cat /etc/passwd | grep /bin/bash | grep -v root | cut -d ":" -f 1)
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do
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useradd -r $i
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done
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9

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while 循环和 until 循环
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while 循环：不定循环，条件循环
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while (条件判断式)
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do
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程序
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30 collapsed lines
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     done
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/dev/null
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stdin $name &i > /dev/null
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#!/bin/bash
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#从1加到100
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i=1
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s=0
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while($i -le 100)
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do
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s=$(($s+$i))
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i=$(($i+1))
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done
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echo "The sum is : $s"
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until 循环:与while 相反
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#!/bin/bash
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i=1
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s=0
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until [$i -gt 100]
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do
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s=$(($s+$i))
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i=$(($i+1))
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done
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echo $s