脚本监听文件夹事件Powershell

Question

I am having problem with a Powershell script. What I am doing in the following lines of code is hopefully clear by STEPS (1)-(4):

# STEP (1) Create listener on folder where outputfile.pdf file will be created 
#         (folder here is `$folder`).

# STEP (2) Wait for new .pdf file to be created.

# STEP (3) When file is created, send mail and print.

# STEP (4) Unsubscribe listener.


$folder = 'X:\foldername'
$filter = '*.*'                             # <-- set this according to your requirements

# STEP (1)

$fsw = New-Object IO.FileSystemWatcher $folder, $filter -Property @{
 IncludeSubdirectories = $false             # <-- set this according to your requirements
 NotifyFilter = [IO.NotifyFilters]'FileName, LastWrite'
}

# Run python script, removing existing .pdf-files.
Write-Host "Running PS-script..."
start-process runrisk.bat -workingdirectory "H:\FX\"

# STEP (2)

$onCreated = Register-ObjectEvent $fsw Created -SourceIdentifier FileCreated -Action {
 $path = $Event.SourceEventArgs.FullPath
 $name = $Event.SourceEventArgs.Name
 $changeType = $Event.SourceEventArgs.ChangeType
 $timeStamp = $Event.TimeGenerated

 # STEP (3)    

 # Call sendMail.ps1 to send mail confirmation
 invoke-expression -Command .\sendMail.ps1
 Write-Host "The file '$name' was $changeType at $timeStamp `r"

 # Print file
 start-process outputfile.pdf -workingdirectory "X:\folder1" -verb Print

 # STEP (4)
 # unregister current subscription
  Unregister-Event -SourceIdentifier FileCreated

}

I have built an .exe-file around this script. If I run this .ps1 file directly from PowerShell, everything works as one would expect: (1) Create listener onto folder, (2) delete old .pdf-file and wait for new .pdf-file to be created, (3) print and send mail on creation-event, (4) unsubscribe listener.

When trying to run the .exe file, or when eg running the ps1-file through Windows Task Scheduler, it seems to only run until STEP (2), ie it seems as though no listener is created, and hence nothing happens when the bat-file creating .pdf-file is finished. It just flashes some cmd-window and that's it.

Any thoughts would be very much grateful!

Thanks, Niklas

Answer 1

Your script executes Register-objectEvent and then immediately stops. So if there will be any event triggered you don't allow the script to wait long enough to see any action associated with that trigger. One way to allow for enough time is to add a line like this to the end of the script:

while ($true) {sleep 5}

The above line lets your script wait for any triggers to occur and the action to take place. See the example on this article .

When you execute your script in a interactive PowerShell window, the register event listener persists after the script terminates, but only as long as you keep the window open. Probably this will let you see the action take place. However as soon as you close the window, the eventlistener will get unregistered automatically and no action will be taken.

I don't know exactly how creating an executable changes this behaviour, but certainly as I understand it, the exe that you create also terminates immediately and doesn't wait for the event to be triggered, which is not the right behaviour to get any results from your script.