Do-While Loop

When we need to run a loop at least once, then we use the Do-while loop in a PowerShell.

The Do-While loop is a looping structure in which a condition is evaluated after executing the statements. This loop is also known as the exit-controlled loop.

The do-while loop is the same as while loop, but the condition in a do-while loop is always checked after the execution of statements in a block.

The Do keyword is also used with the 'Until' keyword to run the statements in a script block. Like a Do-while loop, the Do-until loop also executes at least once before the condition is evaluated. The Do-Until loop executes its statements in a code block until the condition is false. When the condition is true, the loop will terminate.

We can use the flow control keywords such as Break and Continue in a Do-while or Do-until loop.

Syntax

The following block shows the syntax of Do-while loop:

Do
{
        Statement-1
        Statement-2
        Statement-N 
} while( test_expression)

The following block shows the syntax of Do-until loop:

Do
{
        Statement-1
        Statement-2
        Statement-N 
} until( test_expression)

Flowchart of Do-While loop

Flowchart of Do-Until loop

Examples

The following examples describe how to use the Do-while and Do-until loop in the PowerShell:

Example1: In this example, we print the values of an integer from 1 to 10.

PS C:\> $i=1
PS C:\> do
>> {
>> echo $i
>> $i=$i+1
>> }while($i -le 10)

Output:

1
2
3
4
5
6
7
8
9
10

Example2: In this example, we will print the values of an array using Do until loop.

PS C:\> $array=1,2,3,4,5,6,7
PS C:\> $i=0
PS C:\> do{
>> echo $array[$i]
>> $i=$i+1
>> } until ($i -eq $array.length)

Output:

1
2
3
4
5
6
7

Example3: In this example, we print the table of 5 by using the Do-while loop.

PS C:\> $table=5
PS C:\> $i=1
PS C:\> do
>> {
>> echo " $table * $i = $res"
>> $i=$i+1
>> }while($i -le 10)

Output:

5 * 1 = 5
5 * 2 = 10
5 * 3 = 15
5 * 4 = 20
5 * 5 = 25
5 * 6 = 30
5 * 7 = 35
5 * 8 = 40
5 * 9 = 45
5 * 10 = 50

In this example, we have printed the multiplication table of 5 using a Do-while loop. First, we have created and initialized a variable $table and $i with the values 5 and 1 respectively. Then we have written a do-while loop.

In a loop, we have an echo command that will print the result of $res, which stores the multiplication of $table * $i.

Each time, the value of the variable $i is increased by 1, and the condition is checked. When the value of variable $i becomes 11, the condition becomes false, and the loop is terminated.