PowerShell: The automatic variable $NULL

$null is an automatic variable. It is the only instance of the null type.

$null is also referred to as null value.

The value of a PowerShell variable that was not assigned a value (yet) is $null. The value of $null itself is the C# value null.

$null can be assigned any value; yet, the value of $null remains unchanged:

PS C:\> $null = mkdir temp-dir
PS C:\> $null

Assigning a value of an expression to $null is typically used to hide the returned result on the console. In order to be more explicit about this intention, some prefer to write mkdir temp-dir | out-null instead.

$null has a count property whose value is 0:

PS C:\> $null.count
0

if ($val -eq $null) {
  'val is null'
} else {
  'val is not null'
}