Linux control Loops

You can control two commands inside the loop: The break command continue command

Break command

The break command is a simple way to jump out of a loop during a process. You can use the break command to jump out of any type of loop, including while loops and until loops

1. Jump out of a single loop

#!/bin/bash

#breaking out of A For loop

For var1 in 1 2 3 4 5

Do

If [$var 1-eq 3]

Then

Break

Fi

echo "Iteration Number: $var 1"

Done

echo "The For loop in completed"

When Var1=3, jump out of the loop!

[Email protected] ~]#./test17.sh

Iteration Number:1

Iteration Number:2

The For loop in completed

2. Jumping inside the loop

#!/bin/bash

#breaking out of an inner loop

For ((a = 1; a < 4; a++))

Do

echo "out side loop: $a"

for ((b = 1; b <; b++))

Do

If [$b-eq 5]

Then

Break

Fi

echo "in loop: $b"

Done

Done

[Email protected] ~]#./test19.sh

Out Side Loop:1

In Loop:1

In Loop:2

In Loop:3

In Loop:4

Out Side Loop:2

In Loop:1

In Loop:2

In Loop:3

In Loop:4

Out Side Loop:3

In Loop:1

In Loop:2

In Loop:3

In Loop:4

3. Jump out of the outer loop: Break n

n indicates the loop level to jump out, the default n=1, which represents jumping out of the current loop! If n=2, the outer loop will be stopped

#!/bin/bash

#breaking out of an outer loo

for ((a = 1; a < 4; a++))

Do

echo "Out Loop: $a"

for ((b = 1; b <100; b++))

Do

If [$b-GT 4]

Then

Break 2

Fi

echo "Inner Loop: $b"

Done

Done

[Email protected] ~]#./test20.sh

Out Loop:1

Inner loop:1

Inner Loop:2

Inner Loop:3

Inner Loop:4

Continue command

Continue is an early stop loop inside the command, rather than completely terminating the loop Method!

#!/bin/bash

#using the Continue command

For ((var1 = 1; var1 <; var1++))

Do

if [$var 1-gt 3] && [$var 1-lt]

Then

Continue

Fi

echo "Iteration Number: $var 1"

Done

[Email protected] ~]#./test21.sh

Iteration Number:1

Iteration Number:2

Iteration Number:3

Iteration Number:10

Iteration Number:11

Iteration Number:12

When the If-then statement condition (with a value greater than 5 less than 10) is met, the shell executes the continue command, skipping the remaining commands in the loop, but the loop continues! If the if-the statement condition is not met, then the loop returns to normal!

As with the break command, the Continue command can also specify the loop level:

Continue N

#!/bin/bash

#testing an outer loop

for ((a = 1; a <= 3; a++))

Do

echo "Iteration $a"

For ((b = 1; b < 4; b++))

Do

If [$a-gt 2] && [$a-lt 4]

Then

Continue 2

Fi

var3=$[$a * $b]

echo "The result of $a * $b is $var 3"

Done

Done

[Email protected] ~]#./test22.sh

Iteration 1

The result of 1 * 1 is 1

The result of 1 * 2 is 2

The result of 1 * 3 is 3

Iteration 2

The result of 2 * 1 is 2

The result of 2 * 2 is 4

The result of 2 * 3 is 6

Iteration 3

Redirect the output of the loop:

#!/bin/bash

for ((a = 1; a <; a++))

Do

echo "The number is $a"

Done > Test23.txt

echo "The command is finished"

[Email protected] ~]#./test23.sh

The command is finished

[email protected] ~]# cat Test23.txt

The number is 1

The number is 2

The number is 3

The number is 4

The number is 5

The number is 6

The number is 7

The number is 8

The number is 9

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Linux Control loops