Nested loops in Linux

Nested loops (inner loop): A loop statement can use any type of command in a loop, including other loop commands

Example 1:

#!/bin/bash

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

Do

echo "Starting loop $a"

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

Do

echo "Inside loop $b"

Done

Done

[Email protected] ~]#./test14.sh

Starting Loop 1

Inside Loop 1

Inside Loop 2

Inside Loop 3

Starting Loop 2

Inside Loop 1

Inside Loop 2

Inside Loop 3

Starting Loop 3

Inside Loop 1

Inside Loop 2

Inside Loop 3

Example 2:

#!/bin/bash

Var1=3

While [$var 1-ge 0]

Do

echo "Outer loop: $var 1"

for ((var2 = 1; $var 2 < 3; var2++))

Do

var3=$[$var 1 * $var 2]

echo "Inner loop: $var 1 * $var 2 = $var 3"

Done

var1=$[$var 1-1]

Done

[Email protected] ~]#./test15.sh

Outer Loop:3

Inner Loop:3 * 1 = 3

Inner Loop:3 * 2 = 6

Outer Loop:2

Inner Loop:2 * 1 = 2

Inner Loop:2 * 2 = 4

Outer loop:1

Inner loop:1 * 1 = 1

Inner loop:1 * 2 = 2

Outer loop:0

Inner loop:0 * 1 = 0

Inner loop:0 * 2 = 0

Example 3:

#!/bin/bash

Var1=3

Until [$var 1-eq 0]

Do

echo "Outer loop: $var 1"

Var2=1

While [$var 2-lt 5]

Do

Var3= ' echo ' scale=4; $var 1/$var 2 "| BC '

echo "Inner loop: $var 1/$var 2 = $var 3"

var2=$[$var 2 + 1]

Done

var1=$[$var 1-1]

Done

[Email protected] ~]#./test16.sh

./test16.sh:line 5:echoouter loop:3: Command not found

Inner loop:3/1 = 3.0000

Inner loop:3/2 = 1.5000

Inner loop:3/3 = 1.0000

Inner Loop:3/4 =. 7500

./test16.sh:line 5:echoouter loop:2: Command not found

Inner loop:2/1 = 2.0000

Inner loop:2/2 = 1.0000

Inner loop:2/3 =. 6666

Inner loop:2/4 =. 5000

./test16.sh:line 5:echoouter loop:1: Command not found

Inner loop:1/1 = 1.0000

Inner loop:1/2 =. 5000

Inner loop:1/3 =. 3333

Inner loop:1/4 =. 2500

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Nested loops in Linux