CODEWITHSUNDEEP
powershellwmi
Josh
Josh

Reputation: 11

Powershell null pointer exception

I've been working on and off on a project to compress and move files older than x days to an archival folder. I've retrofitted the script here: https://gallery.technet.microsoft.com/scriptcenter/PowerShell-Compress-Log-121e63b5 to assist me however I'm running into an issue that has proved fairly annoying.

When I run this on my machine, utilizing local directories, the script completes as expected. However, when I pass networked file paths to the script, the Get-WmiObject query begins returning null results.

For example, this is a sample command line that works:

powershell -executionpolicy remotesigned -File compress_and_move_files.ps1 c:\temp\ c:\temp\compress_test\ 14

When I move to a UNC path, I begin getting the null-valued expression error on the WMIQuery.Compress() call

powershell -executionpolicy remotesigned -File compress_and_move_files.ps1 \\server1\temp\ \\server1\temp\compress_test\ 14

This is the full error:

You cannot call a method on a null-valued expression.
At compress_and_move_files.ps1:14 char:23
+ If ($WMIQuery.Compress <<<< ()) {Write-Host "$FullName compressed successfull
y."-ForegroundColor Green}
    + CategoryInfo          : InvalidOperation: (Compress:String) [], RuntimeE
   xception
    + FullyQualifiedErrorId : InvokeMethodOnNull

Upvotes: 1

Views: 694

Answers (1)

Mathias R. Jessen
Mathias R. Jessen

Reputation: 174445

That script attempts to retrieve a CIM_DataFile instance - a class that isn't accessible via UNC paths in WMI.

Change the script to target the remote computer and then use the local file system path:

$Server   = "server1"
$WMIFile  = "C:\temp\".Replace("\", "\\")
$WMIQuery = Get-WmiObject -Computer $Server -Query "SELECT * FROM CIM_DataFile WHERE Name='$WMIFileName'"

Upvotes: 2

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