Why "Write-Host" works differently from PowerShell function and timer handler?

Question

I have 1809 Windows 10 box with PowerShell Core 6.1.1 Given following code sample:

function Test() {
  Write-Host "Test"
}
function Invoke-Test() {
  $timer = New-Object System.Timers.Timer
  $timer.AutoReset = $false
  $timer.Interval = 1
  Register-ObjectEvent -InputObject $timer -EventName Elapsed -Action {
    Test
  }
  $timer.Enabled = $true
}

If I invoke "Test" function, I get "Test" output as expected:

But if I schedule invocation with a timer, command prompt is completely messed up:

I vaguely understand that it's something related to internal "readline" and console mechanic, but is it any way to produce newline output followed by a command prompt from a timer/handle in powershell?

user_10844791 · Answer

Register-ObjectEvent -InputObject $timer -EventName Elapsed -SourceIdentifier Timer.Test -Action {
    Test
  }

$timer.Enabled = $true

PS C:\> $Subscriber = Get-EventSubscriber -SourceIdentifier Timer.Test
PS C:\> $Subscriber.action | Format-List -Property *

The command property should hold the results of your “test” function.

The url below has detailed explanations. https://docs.microsoft.com/en-us/powershell/module/microsoft.powershell.utility/get-eventsubscriber?view=powershell-6

Why "Write-Host" works differently from PowerShell function and timer handler?

1 Answers