Welcome PowerShell User! This recipe is just one of the hundreds of useful resources contained in the PowerShell Cookbook.

If you own the book already, login here to get free, online, searchable access to the entire book's content.

If not, the Windows PowerShell Cookbook is available at Amazon, or any of your other favourite book retailers. If you want to see what the PowerShell Cookbook has to offer, enjoy this free 90 page e-book sample: "The Windows PowerShell Interactive Shell".

Mastodon: @Lee_Holmes | Mail: lee/leeholmes.com

4.2 Adjust Script Flow Using Conditional Statements

Problem

You want to control the conditions under which PowerShell executes commands or portions of your script.

Solution

Use PowerShell’s if, elseif, and else conditional statements to control the flow of execution in your script.

For example:

$temperature = 90

if($temperature -le 0)
{
   "Balmy Canadian Summer"
}
elseif($temperature -le 32)
{
   "Freezing"
}
elseif($temperature -le 50)
{
   "Cold"
}
elseif($temperature -le 70)
{
   "Warm"
}
else
{
   "Hot"
}

Discussion

Conditional statements include the following:

if statement

Executes the script block that follows it if its condition evaluates to true

elseif statement

Executes the script block that follows it if its condition evaluates to true and none of the conditions in the if or elseif statements before it evaluate to true

else statement

Executes the script block that follows it if none of the conditions in the if or elseif statements before it evaluate to true

In addition to being useful for script control flow, conditional statements are often a useful way to assign data to a variable. PowerShell makes this very easy by letting you assign the results of a conditional statement directly to a variable:

$result = if(Get-Process -Name notepad) { "Running" } else { "Not running" }

For very simple conditional statements such as this, you can also use PowerShell’s ternary operator:

$result = (Get-Process -Name notepad*) ? "Running" : "Not running"

For more information about these flow control statements, type Get-Help about_If.