PowerShell: Accessing Environment Variables

Accessing environment variables via PowerShell is very simple. 🎬 I also created a video on this topic.

Read an environment variable via the $Env: variable

The simplest way is through the $Env: variable. Just type $Env, then a colon, and then the name of the environment variable whose value you want to read.

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$Env:username

This outputs the username of the currently logged-in user.

This also works cross-platform, for example on Linux.

Read environment variables via a PSDrive

Environment variables are also available as a PSDrive, meaning as a PowerShell drive. That means you can navigate through all environment variables just like through a file system. For example, you can list all environment variables with Get-ChildItem.

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Get-ChildItem Env:

This gives you a nice listing of all environment variables and their values. This also works cross-platform, for example on Linux.

Scopes of environment variables

On Windows there are three scopes for environment variables (English: scopes):

• Machine scope (sometimes also called System scope)
• User scope
• Process scope

These three scopes form a hierarchy, and values set there are inherited downward unless they are overridden at a lower level. In the screenshot below, for example, the variable “TEMP” is set system-wide to C:\Windows\Temp. But in the user scope it is overridden by C:\Users\diecknet\AppData\Local\Temp.

In addition, it can also be overridden at the process level. In PowerShell I can simply use a $Env: variable and assign a different value.

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$Env:TEMP = "C:\TEMP"

For this PowerShell process, the value is then different. Subordinate processes will also be started with the modified environment variables.

If we want to change an environment variable not only for the current process scope, but for the user scope or the system scope, it is not as simple as a normal variable assignment in PowerShell.

Setting environment variables in other scopes

To set user-scope or system-scope environment variables, we can use a .NET method, namely:

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[System.Environment]::SetEnvironmentVariable("Name","Value","Scope")

Possible values for the scope are Machine, User, or Process. If you want to make a system-wide change, meaning a variable in the Machine scope, you need administrator rights, otherwise the operation will fail.

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# Example to set an environment variable in the Machine scope
[System.Environment]::SetEnvironmentVariable("Hello","TEST","Machine")

# Example to set an environment variable in the User scope
[System.Environment]::SetEnvironmentVariable("Hello","TEST","User")

Note: If you make a change for one of these higher levels, it will not automatically be inherited by the currently running PowerShell process. The environment variables are loaded when the process starts.

Deleting an environment variable

If you want to delete an environment variable, you can simply set it to an empty value. This works with both the $Env: syntax and the .NET method.

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# Delete an environment variable using the .NET method
[System.Environment]::SetEnvironmentVariable("Channel","","User")

# Delete an environment variable using the $Env: syntax
$Env:Test123 = ""
# Delete an environment variable using the $Env: syntax (this also works)
$Env:Test123 = $null