PowerShell - wrong array length/count (1 when empty) [duplicate] - powershell

Question

This question already has answers here:
Eliminate Nulls
(2 answers)
Closed 3 years ago.
I essentially have an array $ServerList which holds a list of array I want to test, while $ExclusionList is a list of servers that have to be exluded.
The code should test the list of server with a Test-Connection and save the unreachable ones in $nonactivearray and remove them from $ServerList.
After that it will remove any entry in $ExclusionList from $ServerList.
If $ServerList becomes and empty array, it will ask the user to type the list of servers.
The code seems to work correctly until a correct server is given.
I found that, although $nonactivearray becomes empty, $nonactivearray.Count or $nonactivearray.Length return 1, hence it will enter in a endless loop since both $ServerList and $nonactivearray have number of elements greater than 0.
# Define function to center the text in the current line (taken from: https://stackoverflow.com/a/48622585/10516690)
function Write-HostCenter {
param($Message)
Write-Host ("{0}{1}" -f (' ' * (([Math]::Max(0, $Host.UI.RawUI.BufferSize.Width / 2) - [Math]::Floor($Message.Length / 2)))), $Message)
}
# Define Test-Connection as a string for Invoke-Expression later
[string]$TestConn = "Test-Connection -Quiet -Count 1 -ComputerName "
# Define excluded servers
$ExclusionList = #("Server1","Server2","Server3")
# Save old progress settings
$OldProgress = $ProgressPreference
$ProgressPreference = 'SilentlyContinue'
# Test Server availability
$nonactivearray = #() # Array of unreachable/excluded servers
$nonactive = "" # String to display the unreachable/excluded doscovered in our list of servers. Probably unnecessary, "$nonactivearray" can be used
$i = 0
foreach ($newserver in $ServerList) {
if (-Not (Invoke-Expression -Command "$TestConn $newserver")) {
$nonactive += $newserver
$nonactivearray += $newserver
if ($i -lt $ServerList.Length) {
$nonactive += " "
}
}
$i++
}
$ProgressPreference = $OldProgress
# List unreachable and excluded servers
$nonactivearray += (Compare-Object -ReferenceObject $ServerList `
-DifferenceObject $ExclusionList `
-ExcludeDifferent -IncludeEqual).InputObject
$nonactive = "$nonactivearray"
$CurPosPing = $host.UI.RawUI.CursorPosition
while ($nonactivearray.Length -ge 1) {
$host.UI.RawUI.CursorPosition = $CurPosPing
Write-Host " These HOSTS are not reachable, hence they will be ignored:"
$TempForegroundColor = $Host.Ui.RawUI.ForegroundColor # <== Temporary solution
$Host.Ui.RawUI.ForegroundColor = "Red" # <== Temporary solution
Write-HostCenter $nonactive # Write-HostCenter defined in a function. It centers the text in the shell
$Host.Ui.RawUI.ForegroundColor = $TempForegroundColor # <== Temporary solution
# Remove unreachable servers with filters
$ServerList = $ServerList | Where-Object {$nonactivearray -notcontains $_}
# Check if the new list is empty
while ($ServerList.Length -lt 1) {
Write-Host " "
$CurPos = $host.UI.RawUI.CursorPosition
Write-Host " The list of server is now empty, please type it now. " -ForegroundColor Yellow
Write-Host " Use the comma `"" -NoNewline; Write-Host "," -NoNewline -ForegroundColor Yellow
Write-Host "`" as a separator (spaces will be ignored)."
Write-Host " "
# Get list from user
# $CurPos = $host.UI.RawUI.CursorPosition
$ServerList = Read-Host -Prompt " Server list"
$ServerList = $ServerList -replace ' ',''
[string[]]$ServerList = $ServerList -split ','
$ServerList = $ServerList | Where-Object {$_.length -gt 0}
while ($ServerList.Length -lt 1) {
$Host.UI.RawUI.CursorPosition = $CurPos
Write-Host " >>> The list is STILL empty, please type it again. <<< " -ForegroundColor Yellow
Write-Host " "
Write-Host " "
# $CurPos = $host.UI.RawUI.CursorPosition
$ServerList = Read-Host -Prompt " Server list"
$ServerList = $ServerList -replace ' ', ''
[string[]]$ServerList = $ServerList -split ','
$ServerList = $ServerList | Where-Object {$_.length -gt 0}
}
}
# Re-check server connectivity
$OldProgress = $ProgressPreference
$ProgressPreference = 'SilentlyContinue'
Write-Host "serverlist"
$ServerList
$nonactivearray = #()
$nonactive = ""
$i = 0
foreach ($newserver in $ServerList) {
if (-Not (Invoke-Expression -Command "$TestConn $newserver")) {
$nonactive += $newserver
$nonactivearray += $newserver
if ($i -lt $ServerList.Length) {
$nonactive += " "
}
}
$i++
}
$ProgressPreference = $OldProgress
$nonactivearray += (Compare-Object -ReferenceObject $ServerList `
-DifferenceObject $ExclusionList `
-ExcludeDifferent -IncludeEqual).InputObject
$nonactive = "$nonactivearray"
}
Thank you and best.
[EDIT]
Sorry, I also forgot the following lines that I have added on the top of the code:
# Define function to center the text in the current line (taken from: https://stackoverflow.com/a/48622585/10516690)
function Write-HostCenter {
param($Message)
Write-Host ("{0}{1}" -f (' ' * (([Math]::Max(0, $Host.UI.RawUI.BufferSize.Width / 2) - [Math]::Floor($Message.Length / 2)))), $Message)
}
# Define Test-Connection as a string for Invoke-Expression later
[string]$TestConn = "Test-Connection -Quiet -Count 1 -ComputerName "
# Define excluded servers
$ExclusionList = #("Server1","Server2","Server3")
I hope I am not forgetting anything else...

Answer 1

Thank you for your help.
I could not fix the issue with the solutions proposed, but you gave me the insight to find a solution.
I searched for "how to remove $null values from an array" and I found this answer from mklement0 in another post.
I tried the following:
PS N:\> $list = #("1","","3","$null","7")
PS N:\> $list
1
3
7
PS N:\> $list -notlike ''
1
3
7
and then added the following line in my code:
$nonactivearray = $nonactivearray -notlike ''
That solved the issue. :)
Thank you again.