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Using Powershell to monitor file changes then execute a command

Posted on 2016-08-03
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Last Modified: 2016-08-04
So I am trying to make a script that monitors a file for changes and then executes Unblock-File cmdlet from Powershell. I have gotten to this point and PowerShell ISE is throwing a lot of errors at me. This is my first run time working with Powershell so I am wondering if I am on the right track or way off base.
 

strComputer = “.”
 
Set objWMIService = GetObject(“winmgmts:” _
 
    & “{impersonationLevel=impersonate}!\\” & _
 
        strComputer & “\root\cimv2”)
 
Set colMonitoredEvents = objWMIService.ExecNotificationQuery _
 
    (“SELECT * FROM __InstanceCreationEvent WITHIN 5 WHERE ” _
 
        & “Targetinstance ISA ‘CIM_DirectoryContainsFile’ and ” _
 
            & “TargetInstance.GroupComponent= ” _
 
                & “‘Win32_Directory.Name=””c:\\\\users\garretth\desktop\unblockfolder\””‘”)
 
Do
 
    Set objLatestEvent = colMonitoredEvents.NextEvent
 
    gci C:\users\garretth\desktop\unblockfolder | Unblock-File
 
Loop
 

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Question by:Garrett
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Accepted Solution

by:
Dustin Saunders earned 500 total points
ID: 41741207
Create a file system watcher to do the unblock.

$folder = 'c:\test\' 
$filter = '*.*'  

$fsw = New-Object IO.FileSystemWatcher $folder, $filter -Property @{IncludeSubdirectories = $false;NotifyFilter = [IO.NotifyFilters]'FileName, LastWrite'} 

Register-ObjectEvent $fsw Created -SourceIdentifier FileCreated -Action { 
$name = $folder + $Event.SourceEventArgs.Name 
Unblock-File $name
} 

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Change $folder with your folder and the $filter if it's only a specific file type.
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Expert Comment

by:Dustin Saunders
ID: 41741209
You can unregister the watcher (turn it off) with:
Unregister-Event FileCreated 

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by:Garrett
ID: 41741622
That you for your response! Super helpful. Is it possible to make it loop or does the $fsw call a Windows service that is always monitoring? My network admin was wondering the system resource use on this as well. It shouldn't be a lot but I was wondering if you had any insight.
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LVL 12

Expert Comment

by:Dustin Saunders
ID: 41741774
You're creating a watcher object, so it will always wait for a file event to occur in the location specified and then trigger (doesn't run like a service or a looping script).  The resource usage is negligible, unless for some reason you are saving and processing thousands of files every few seconds; but I'm guessing based off the unblock command you're just downloading office files you want unblocked.
1
 
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Author Comment

by:Garrett
ID: 41742367
You're correct about the office files!
Thank you so much. I appreciate your help and explanation!
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