本篇主要写一些shell脚本循环语句的使用。

---

for 循环

指定次数

#!/bin/bash

for ((i=1;i<=10;i++))

do

  echo $i

done

[root@localhost ~]# vim num.sh

[root@localhost ~]# chmod +x num.sh

[root@localhost ~]# ./num.sh

1

2

3

4

5

6

7

8

9

10

• 九九乘法口诀表

#!/bin/bash

result=0

for ((i=1;i<=9;i++))

do

  for ((j=1;j<=$i;j++))

  do

    result=`expr $i \* $j`

    echo -en "$j * $i = $result\t"

  done

  echo ""

done

[root@localhost ~]# vim 99.sh

[root@localhost ~]# ./99.sh

1 * 1 = 1

1 * 2 = 2	2 * 2 = 4

1 * 3 = 3	2 * 3 = 6	3 * 3 = 9

1 * 4 = 4	2 * 4 = 8	3 * 4 = 12	4 * 4 = 16

1 * 5 = 5	2 * 5 = 10	3 * 5 = 15	4 * 5 = 20	5 * 5 = 25

1 * 6 = 6	2 * 6 = 12	3 * 6 = 18	4 * 6 = 24	5 * 6 = 30	6 * 6 = 36

1 * 7 = 7	2 * 7 = 14	3 * 7 = 21	4 * 7 = 28	5 * 7 = 35	6 * 7 = 42	7 * 7 = 49

1 * 8 = 8	2 * 8 = 16	3 * 8 = 24	4 * 8 = 32	5 * 8 = 40	6 * 8 = 48	7 * 8 = 56	8 * 8 = 64

1 * 9 = 9	2 * 9 = 18	3 * 9 = 27	4 * 9 = 36	5 * 9 = 45	6 * 9 = 54	7 * 9 = 63	8 * 9 = 72	9 * 9 = 81

遍历循环

#!/bin/bash

TMP=$(cat username.txt)

for USER in $TMP

do

  echo "用户：$USER"

done

[root@localhost ~]# vim users.sh

[root@localhost ~]# chmod +x users.sh

[root@localhost ~]# vim users.txt

[root@localhost ~]# cat users.txt

zhangsan

lisi

wangwu

[root@localhost ~]# ./users.sh

用户：zhangsan

用户：lisi

用户：wangwu

• 添加用户

#!/bin/bash

TMP=$(cat users.txt)

for USER in $TMP

do

  useradd $USER && echo "123456" | passwd --stdin $USER &> /dev/null

done

echo "添加的用户信息为："

tail -$(cat users.txt | wc -l) /etc/passwd

for USER in $TMP

do

  userdel -r $USER

done

echo "已删除添加的用户"

[root@localhost ~]# vim useradd.sh

[root@localhost ~]# chmod +x useradd.sh

[root@localhost ~]# ./useradd.sh

添加的用户信息为：

zhangsan:x:1001:1001::/home/zhangsan:/bin/bash

lisi:x:1002:1002::/home/lisi:/bin/bash

wangwu:x:1003:1003::/home/wangwu:/bin/bash

已删除添加的用户

• 检查主机状态

#!/bin/bash

TMP=$(cat ipadds.txt)

for IP in $TMP

do

  ping -c 4 -i 0.2 -W 3 $IP &> /dev/null

  if [ $? -eq 0 ]

  then

    echo "Host $IP is up"

  else

    echo "Host $IP is down"

  fi

done

[root@localhost ~]# vim ping.sh

[root@localhost ~]# chmod +x ping.sh

[root@localhost ~]# vim ipadds.txt

[root@localhost ~]# cat ipadds.txt

127.0.0.1

192.168.28.129

[root@localhost ~]# ./ping.sh

Host 127.0.0.1 is up

Host 192.168.28.129 is down

while 循环

• 输出1到10

#!/bin/bash

num=1

while [ $num -le 10 ]

do

  echo $num

  #num=`expr $num + 1`

  let num++

done

• 添加用户

#!/bin/bash

# useradd

num=1

while [ $num -le 10 ]

do

  useradd stu$num && echo "123456" | passwd --stdin stu$num &> /dev/null

  let num++

done

echo "添加的用户信息为："

tail -10 /etc/passwd

# userdel

num=1

while [ $num -le 10 ]

do

  userdel -r stu$num

  let num++

done

echo "已删除添加的用户"

[root@localhost ~]# vim useradd10.sh

[root@localhost ~]# ./useradd10.sh

添加的用户信息为：

stu1:x:1001:1001::/home/stu1:/bin/bash

stu2:x:1002:1002::/home/stu2:/bin/bash

stu3:x:1003:1003::/home/stu3:/bin/bash

stu4:x:1004:1004::/home/stu4:/bin/bash

stu5:x:1005:1005::/home/stu5:/bin/bash

stu6:x:1006:1006::/home/stu6:/bin/bash

stu7:x:1007:1007::/home/stu7:/bin/bash

stu8:x:1008:1008::/home/stu8:/bin/bash

stu9:x:1009:1009::/home/stu9:/bin/bash

stu10:x:1010:1010::/home/stu10:/bin/bash

已删除添加的用户

• 猜数字游戏

RANDOM值的范围为：0-32767

#!/bin/bash

key=$(expr $RANDOM % 1000)

times=0

while true

do

  read -p "请输入数字(0-999)：" num

  let times++

  if [ $num -eq $key ]

  then

    echo "猜对了！你猜了 $times 次。"

    exit 0

  elif [ $num -gt $key ]

  then

    echo "猜高了"

  else

    echo "猜低了"

  fi

done

[root@localhost ~]# vim guess.sh

[root@localhost ~]# chmod +x guess.sh

[root@localhost ~]# ./guess.sh

请输入数字(0-999)：500

猜低了

请输入数字(0-999)：750

猜低了

请输入数字(0-999)：875

猜高了

请输入数字(0-999)：800

猜低了

请输入数字(0-999)：850

猜高了

请输入数字(0-999)：825

猜低了

请输入数字(0-999)：835

猜低了

请输入数字(0-999)：840

猜高了

请输入数字(0-999)：838

猜对了！你猜了 9 次。

综合实例

• 购物系统

#!/bin/bash

# Shopping System V1.1

c1=手套

c2=外套

c3=裤子

c4=鞋子

p1=40

p2=500

p3=150

p4=200

count=0

total=0

echo "欢迎光临！物美价廉！欢迎选购！"

for ((i=1;i<=5;i++))

do

  read -p "第 $i 家店，是否进入(y/n)：" ack

  if [ $ack = y ]

  then

    echo "商品如下："

    echo "1.$c1：￥$p1"

    echo "2.$c2：￥$p2"

    echo "3.$c3：￥$p3"

    echo "4.$c4：￥$p4"

    while true

    do

      read -p "是否购买(y/n)：" ack

      if [ $ack = y ]

      then

        read -p "请输入需要购买的商品序号：" num

        case $num in

        1)

          echo "您购买了$c1"

          let count++

          total=`expr $total + $p1`

          ;;

        2)

          echo "您购买了$c2"

          let count++

          total=`expr $total + $p2`

          ;;

        3)

          echo "您购买了$c3"

          let count++

          total=`expr $total + $p3`

          ;;

        4)

          echo "您购买了$c4"

          let count++

          total=`expr $total + $p4`

          ;;

        *)

          echo "输入错误，购买失败"

        esac

      elif [ $ack = n ]

      then

        echo "您走出了第 $i 家店"

        break

      else

        echo "输入错误，请重新输入"

      fi

    done

  elif [ $ack = n ]

  then

    continue

  else

    echo "输入错误，请重新输入"

    let i--

  fi

done

echo "购物数量：$count"

echo "购物总价：$total"

echo "感谢您的光临！欢迎下次再来！"