Filesystemwatcher file created event not decompressing files - powershell

Question

I got a simple script that should watch for new files in specified folder and uncompress them on arriving. Simple, but my script only works under the debugger of Powershell ISE. When outside the debugger, on file creation it only prints "New file xxx found" and "Done", without decompressing it, nor deleting, but also no errors. I'm I missing something here?
# Folder you to monitor
$PathToMonitor = "C:\tmp1".
$OutputPath = "C:\tmp"
$Filter = "*.zip" # Filter for zip files.
$FileSystemWatcher = New-Object System.IO.FileSystemWatcher
$FileSystemWatcher.Path = $PathToMonitor
$FileSystemWatcher.IncludeSubdirectories = $false
$FileSystemWatcher.Filter = $Filter
# make sure the watcher emits events
$FileSystemWatcher.EnableRaisingEvents = $true
# define the code that should execute when a file change is detected
$Action = {
$details = $event.SourceEventArgs
$FullPath = $details.FullPath
$OldName = $details.OldName
$Timestamp = $event.TimeGenerated
try
{
Write-Host "New file " + $FullPath + " found"
$TarProgram = "tar.exe"
$TarArgs = 'xvf "' + $FullPath + '" -C ' + $OutputPath
Start-Process $TarProgram $TarArgs -Wait -WindowStyle hidden
Remove-Item -Path $FullPath -Force
Write-Host "Done"
}
catch [System.SystemException]
{
Write-Host $_.ScriptStackTrace
}
}
# add event handlers
$handlers = . {
Register-ObjectEvent -InputObject $FileSystemWatcher -EventName Created -Action $Action -SourceIdentifier FSCreateFtpGe
}
Write-Host "Watching for changes to $PathToMonitor"
try
{
do
{
Wait-Event -Timeout 10
} while ($true)
}
catch [System.SystemException]
{
Write-Host $_.ScriptStackTrace
}
finally
{
# this gets executed when user presses CTRL+C
# remove the event handlers
Write-Host "Cleaning up"
Unregister-Event -SourceIdentifier FSCreateFtpGe
# remove background jobs
$handlers | Remove-Job
# remove filesystemwatcher
$FileSystemWatcher.EnableRaisingEvents = $false
$FileSystemWatcher.Dispose()
"Event Handler disabled."
}

Answer 1

Why do you have a period here...
$PathToMonitor = "C:\tmp1".
...that is invalid syntax and the script should fail anyway. Yet, that could be just a type you did on posting here.
Why are you using tar vs the PowerShell built-in archive cmdlets?
if tar.exe is not in your PowerShell or system paths, you have to fully qualify that path to it for it to be used.
$TarProgram = 'C:\ProgramFiles\tar.exe'
So, your code should work in any PowerShell host (ISE [in/out of debug mode])/powershell.exe/VSCode, et al. AS I just tested it. Yet again, the cmdlets are there. Example of the below running in the new Windows Terminal.
#region Begin Script
# Folder you to monitor
$PathToMonitor = 'D:\tmp1'
$OutputPath = 'D:\tmp'
$Filter = '*.zip' # Filter for zip files.
$FileSystemWatcher = New-Object System.IO.FileSystemWatcher
$FileSystemWatcher.Path = $PathToMonitor
$FileSystemWatcher.IncludeSubdirectories = $false
$FileSystemWatcher.Filter = $Filter
# make sure the watcher emits events
$FileSystemWatcher.EnableRaisingEvents = $true
# define the code that should execute when a file change is detected
$Action = {
$details = $event.SourceEventArgs
$FullPath = $details.FullPath
$OldName = $details.OldName
$Timestamp = $event.TimeGenerated
try
{
"New file $FullPath found"
Expand-Archive -Path $FullPath -DestinationPath 'D:\tmp'
# Start-Process $TarProgram $TarArgs -Wait -WindowStyle hidden
Remove-Item -Path $FullPath -Force
'Done'
}
catch [System.SystemException]
{$PSItem.ScriptStackTrace}
}
# add event handlers
$handlers = . {
$RegisterObjectEventSplat = #{
InputObject = $FileSystemWatcher
EventName = 'Created'
Action = $Action
SourceIdentifier = 'FSCreateFtpGe'
}
Register-ObjectEvent #RegisterObjectEventSplat
}
"Watching for changes to $PathToMonitor"
try
{
do { Wait-Event -Timeout 10 }
while ($true)
}
catch [System.SystemException]
{$_.ScriptStackTrace}
finally
{
<#
this gets executed when user presses CTRL+C
remove the event handlers
#>
'Cleaning up'
Unregister-Event -SourceIdentifier FSCreateFtpGe
# remove background jobs
$handlers |
Remove-Job
# remove filesystemwatcher
$FileSystemWatcher.EnableRaisingEvents = $false
$FileSystemWatcher.Dispose()
'Event Handler disabled.'
}
#endregion End Script
# Results
Get-CimInstance -ClassName Win32_OperatingSystem | Select-Object -Property Caption, Version
Caption Version
$PSVersionTable
Name Value
---- -----
PSVersion 5.1.18362.752
PSEdition Desktop
PSCompatibleVersions {1.0, 2.0, 3.0, 4.0, 5.0, 5.1.18362.752}
BuildVersion 10.0.18362.752
CLRVersion 4.0.30319.42000
WSManStackVersion 3.0
PSRemotingProtocolVersion 2.3
Get-ChildItem -Path 'D:\tmp' -Verbose
(Get-ChildItem -Path 'D:\tmp').Count
0
Get-ChildItem -Path 'D:\tmp1' -Verbose
(Get-ChildItem -Path 'D:\tmp1').Count
0
.\FSWCopyUnzip.ps1
Watching for changes to D:\tmp1
New file D:\tmp1\book1.zip found
Done
Cleaning up
Get-ChildItem -Path 'D:\tmp' -Verbose
Directory: D:\tmp
Mode LastWriteTime Length Name
---- ------------- ------ ----
-a---- 13-Mar-20 12:19 70 abc.txt
-a---- 13-Mar-20 22:27 71 book1.txt
-a---- 06-Apr-20 21:51 2979 Data.zip
-a---- 04-Mar-20 01:04 72 FileWithLines.txt
Get-ChildItem -Path 'D:\tmp1' -Verbose
(Get-ChildItem -Path 'D:\tmp1').Count
0

Answer 2

Just for the records, I found the issue. It's somehow related to variables scopes in Powershell.
If instead of using a variable declared at the begin of the script to hold the value of $OutputPath I use a literal string then it works. Otherwise, it complains that the value is null at runtime (In Powershell ISE it shows a value)
So, the action block now looks like this:
$Action = {
$details = $event.SourceEventArgs
$FullPath = $details.FullPath
$OldName = $details.OldName
$Timestamp = $event.TimeGenerated
try
{
Expand-Archive -LiteralPath $FullPath -DestinationPath "C:\Temp"
Remove-Item -LiteralPath "$FullPath" -Force
}
catch [System.SystemException]
{
Write-Host $_
}
}
I would prefer to have all my vars at the begin, so they can be easily changed if needed, but at least this version works.