Shell's for, while loop

One, for loop

[email protected] shell]# cat for.sh

#!/bin/bash

For i in ' seq 1 10 '; Do

echo "$i"

Done

With this script you can see the basic structure of the For loop:

The condition of the for variable name in the loop; do Commanddone

[Email protected] shell]# sh for.sh

1

2

3

4

5

6

7

8

9

10

Example 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

Example 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

Reference system commands need to be inverted, others do not

[[email protected] shell]# for I in 1 4 5 3 A; Do echo "$i"; Done

1

4

5

3

A

A

Second, while loop

[email protected] shell]# cat while.sh

#!/bin/bash

A=6

While [$a-ge 1]; Do

Echo $a

a=$[$a-1]

Done

The while loop format is also simple:

While condition; Do Commanddone

[Email protected] shell]# sh while.sh

6

5

4

3

2

1

Example 2

[email protected] shell]# cat while2.sh

#!/bin/bash

While:; Do

Seq 1 3

Done

Replace the loop condition with a colon, so that you can do a dead loop

[Email protected] shell]# sh while2.sh

1

2

3

1

2

3

1

2

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Shell's for, while loop