shell之for、while迴圈

標籤：shell

一、for迴圈

[[email protected] shell]# cat for.sh 

#!/bin/bash

for i in `seq 1 10`; do

echo "$i"

 done

通過這個指令碼就可以看到for迴圈的基本結構:

for 變數名 in 迴圈的條件； do     commanddone

[[email protected] shell]# sh for.sh

1

2

3

4

5

6

7

8

9

10

例2：

[[email protected] shell]# cat for2.sh

#!/bin/bash

for a in `ls`; do

echo "$a"

done

[[email protected] shell]# sh for2.sh

case1.sh

case.sh

for2.sh

for3.sh

for.sh

if1.sh

if.sh

例3

[[email protected] shell]# cat for3.sh

#!/bin/bash

for file in `vmstat`; do

echo "$file"

done

for i in `cd /shell && ls`; do 

echo "$i"

done

引用系統命令需要加反引號，其他不用

[[email protected] shell]# for i in 1 4 5 3 a a; do echo "$i"; done

1

4

5

3

a

a

二、while迴圈

[[email protected] shell]# cat while.sh 

#!/bin/bash

a=6

while [ $a -ge 1 ]; do

echo $a

a=$[$a-1]

done

while 迴圈格式也很簡單:

while  條件; do          commanddone

[[email protected] shell]# sh while.sh 

6

5

4

3

2

1

例2

[[email protected] shell]# cat while2.sh 

#!/bin/bash

while :; do

seq 1 3

done

把迴圈條件拿一個冒號替代，這樣可以做到死迴圈

[[email protected] shell]# sh while2.sh 

1

2

3

1

2

3

1

2

本文出自 “不變的時光---胡” 部落格，轉載請與作者聯絡！

shell之for、while迴圈