PowerShell Loops Explained

 Powershell loops (for, foreach, and foreach-object) when you there is a need to execute the sequence code for several times to complete a task.

Powershell For loop syntax and examples:

for (<Init>; <Condition>; <Repeat>)

{ <your statement list>}

# Example1

for($i = 0; $i -le 10; $i++)
{
"$i"
}

# Example2

for (($i = 0), ($r = 0); $i -lt 10 -and $r -lt 10; $i++,$r++)
{
    "`$i:$i"
    "`$r:$r"
}

Powershell Foreach loop syntax and examples:

The foreach loop is used for executing code against a series of array objects stored in a variable and during each cycle, the ForEach operator executes a {Statement Block} on each individual item.

Syntax

ForEach  (oneitem In collection) {ScriptBlock}

Oneitem: it’s one of the element or object of collection variable.

Collection:  a series of array objects.

ScriptBlock:  A block of the script runs against each object.

# example1 

$serverlist =  @ ("server1" ," server2", "server3")

Foreach ($server in $serverlist)
{
	Write-host "Servername is" $server
	Invoke-command -computername $server -scriptblock {Get-service -name raj}
}
# example2

foreach ($num in 1,2,3,4,5)
{
	Write-host " my number is" $num
	
}

Powershell Foreach-object  loop syntax and examples:

This foreach-object uses pipeline to executes the task, it takes input objects from the pipeline and runs against each item in the collection.

Syntax

ForEach-Object [-process] ScriptBlock[] [-inputObject psobject]

#Example1:
$names = @("raj","shekar","prava","aryan")
$names | ForEach-Object {
"Hello, my name is $_!"
}

#Example2:
get-childitem  -path "C:\windows" | foreach-object -process { $_.length / 1024 }

Powershell While loop syntax and examples:

This while loop runs a command block based on the result of a conditional test given.

Syntax:

while (condition) {command_block}

# count to 20

$count = 0
While ($count  -ne 20)
{
	$count ++
	Write-host $count
}

Powershell DO loop syntax and examples:

Do-loops  is used when you want to run a codeblock at least once.  A Do-loop evaluates the condition

after executing the code block, unlike a while-loop which does it before executing the code block.

Syntax:

Do

{

code_block

}

while (condition)

I’m learning PowerShell today!

Loop until the condition is true, in other words, loop while the condition is false:

# Examples:

$i = 0
Do {
$i++
"item is $i"
}
 while ($i -ne 3)

$i= 0
Do 
{
$i++
"item is $i"
} 
until ($i -eq 3)

Powershell Switch loop statement.

This switch statement provides a variable and a list of possible values, when the values match the given variable inside statement then its script block will be executed.

Example:

switch ( $today )

    {

        0 { $myday = 'Sunday'    }

        1 { $myday = 'Monday'    }

        2 { $myday = 'Tuesday'   }

        3 { $myday = 'Wednesday' }

        4 { $myday = 'Thursday'  }

        5 { $myday = 'Friday'    }

        6 { $myday = 'Saturday'  }

    }

 $today=  Read-Host "Choose the number"

  Write-Host "Your day is" $myday

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