Get-PSCallStack returns a so-called “Call Stack” which – in its simplest form – tells you the nesting depth of your code: there will be a new object added to the stack each time you enter a script block. Have a look:

function test1
{
    $callstack = Get-PSCallStack
    $nestLevel = $callstack.Count - 1   
    "TEST1: Nest Level: $nestLevel"    
    test2
}

function test2
{
    $callstack = Get-PSCallStack
    $nestLevel = $callstack.Count - 1
    "TEST2: Nest Level: $nestLevel"    
}

# calls test1 which in turn calls test2
test1
# calls test2 directly
test2

In this sample, you have two functions which use Get-PSCallStack to determine their “nest level”. When you run test1, it in turn runs test2, so test2 is running at nest level 2. When you call test2 directly, however, it runs at nest level 1:

 
TEST1: Nest Level: 1
TEST2: Nest Level: 2
TEST2: Nest Level: 1
 

Here is a more useful example of the same technique: a recursive function call that stops at a nest level of ten:

function testRecursion
{
    $callstack = Get-PSCallStack
    $nestLevel = $callstack.Count - 1
    "TEST3: Nest Level: $nestLevel"
    
    # function calls itself if nest level is below 10
    if ($nestLevel -lt 10) { testRecursion }

}

# call the function
testRecursion

Here is the result:

 
TEST3: Nest Level: 1
TEST3: Nest Level: 2
TEST3: Nest Level: 3
TEST3: Nest Level: 4
TEST3: Nest Level: 5
TEST3: Nest Level: 6
TEST3: Nest Level: 7
TEST3: Nest Level: 8
TEST3: Nest Level: 9
TEST3: Nest Level: 10
 

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