Powershell "select -First 0" behaviour

Question

Can anyone explain what's occurring in the case of select -first 0 example in the code below?

Function Test-Example {
    [CmdletBinding()]
    param (
        [Parameter(ValueFromPipeline = $true)]
        $InputObject
    )
    process {
        $global:x++
        write-verbose 'I''m running!'
        $InputObject
    }
}

[int]$global:x = 0 #reset the counter
1..100 | Test-Example -Verbose | select -first 10
$global:x #outputs 10

$global:x = 0 #reset the counter
1..100 | Test-Example | select -first 1000
$global:x #outputs 100; as we only iterate 100 times depsite asking for the first 1000

$global:x = 0 #reset the counter
1..100 | Test-Example | select -first 0 
$global:x #outputs 100; which doesn't make sense since we don't see any output, suggesting `select -first 0` behaves like `select * | out-null`.

If we add the -verbose switch we see that the value of $global:x matches the number of iterations according to the verbose output (i.e. we get 10 verbose messages in the first example, 100 in the second, and 100 in the third).

Answer 1

Select-Object -First 0 or Select-Object -Last 0

Actually the cmdlets internally have a check for this exact scenario and intentionally outputs nothing.

the reason why you are seeing I'm running! for 100 times is Write-Verbose is in Porcess() block. All 100 items get processed and outputs nothing as the code internally skips on the check $this.First != 0 then Skipp