Powershell FileSystemWatcher - Avoiding duplicate action on Create - powershell

Question

It's a known issue in Powershell that the FileSystemWatcher fires twice on events. I am trying to work around this as I am watching for files being created and then pushing it to a printer. The double firing means I am getting duplicated printouts
I know this question has been asked before but I am a complete newb when it comes to Powershell (and scripting in general really) so some of the answers have gone straight over my head
In the code, I am watching a folder and then passing the subdirectory names as the printer name for sending the job. This is because the software in use is copying the pdf files from a remote location into those folders (the software doesn't have direct access to the printers due to citrix)
### SET FOLDER TO WATCH + FILES TO WATCH + SUBFOLDERS YES/NO
$watcher = New-Object System.IO.FileSystemWatcher
$watcher.Path = "L:\Label\"
$watcher.Filter = "*.*"
$watcher.IncludeSubdirectories = $true
$watcher.EnableRaisingEvents = $true
### DEFINE ACTIONS AFTER AN EVENT IS DETECTED
$action = { $path = $Event.SourceEventArgs.FullPath
$changeType = $Event.SourceEventArgs.ChangeType
$printer = Split-Path (Split-Path $path -Parent) -Leaf
$logline = "$(Get-Date), $changeType, $path, $printer"
Add-content "c:\prog\log.txt" -value $logline
C:\prog\SumatraPDF.exe -print-to "\\http://srv:631\$printer" $path
}
### DECIDE WHICH EVENTS SHOULD BE WATCHED
Register-ObjectEvent $watcher "Created" -Action $action
while ($true) {sleep 5}
I expect to see the printing command (the Sumatra call) only occur once when a pdf file is dropped into the watch folder

Answer 1

Instead of telling you what you should or shouldn't do, here is how to do what you asked for:
### SET FOLDER TO WATCH + FILES TO WATCH + SUBFOLDERS YES/NO
$global:canDoEvent = $True #NEW
$watcher = New-Object System.IO.FileSystemWatcher
$watcher.Path = "L:\Label\"
$watcher.Filter = "*.*"
$watcher.IncludeSubdirectories = $true
$watcher.EnableRaisingEvents = $true
DEFINE ACTIONS AFTER AN EVENT IS DETECTED
$action = { if ($global:canDoEvent) { #NEW
$global:canDoEvent = $False #NEW
$path = $Event.SourceEventArgs.FullPath
$changeType = $Event.SourceEventArgs.ChangeType
$printer = Split-Path (Split-Path $path -Parent) -Leaf
$logline = "$(Get-Date), $changeType, $path, $printer"
Add-content "c:\prog\log.txt" -value $logline
C:\prog\SumatraPDF.exe -print-to "\\http://srv:631\$printer" $path
}
}
DECIDE WHICH EVENTS SHOULD BE WATCHED
Register-ObjectEvent $watcher "Created" -EventName newFile -Action $action #NEW
do { #NEW
$global:canDoEvent = $True
Wait-Event -SourceIdentifier newFile -Timeout 1
} while ($True)
It probably requires tuning, I'm no expert, but that's the idea.
Basically, add a global boolean var = True, put your wait-event on a timeout inside a do-while loop, make variable true every loop, then in your event action, make it false. your timeout will define how often the event can fire. a single second should suffice to prevent multiple firing events. Obviously, if there are contexts where more than 1 unique file could be created and printed during the same second, it would skip them.

Answer 2

I don't think it's a known issue that the FileSystemWatcher fires twice on events, not where you got that information.
Regardless, if I were you I wouldn't code the FileSystemWather events in Powershell myself, it's a real pain.
Instead, you can use Powershell Guard, just pass the print command instead of the TestCommand. https://github.com/smurawski/PowerShellGuard
All that PowerGuard does is abstract the use of the FileSystemWatcher. You can create your print command in a Powershell script, and just have PowerGuard call your script with -TestCommand "Print.ps1 .\PathToYourFile"
Final Solution (by the poster himself):
dir \\srv\label\prnlblCuts\*.pdf | New-Guard -TestCommand "C:\PROG\SumatraPDF.exe -print-to \\srv-tsv:631\prnlblCuts" -TestPath "$($_.FullName)" -Wait