Enterprise Admins.org

When I first started with powershell, I converted some functions from a VBscript template I used into powershell code. One of those functions used WMI to create a process on a remote machine and then return the process ID that was created. The function is included at the end of this post.

Last week I worked with a colleague who was using a slightly modified version of this function. It was working fine for most processes, but in one particular case the process was failing on the remote Windows 2003 machine with an out of memory exception. If someone logged into the remote box and ran the process locally it would work fine. The function doesn’t define anything special about memory limits, so I started looking into the win32_process to see if there were memory limits that could be configured. Fortunately I was able to find this article http://blogs.technet.com/b/askperf/archive/2008/09/16/memory-and-handle-quotas-in-the-wmi-provider-service.aspx that discusses this specific issue. We ended up chaing the MemoryPerHost value from 134217728 (128MB) to 1073741824 (1024MB) and the process was able to complete.

Function Start-WmiProcess ($computer, $cmd) {
	$scope = New-Object management.managementscope "\\$computer\root\cimv2"
	$scope.Connect()
	$mp = new-object management.managementpath "win32_process"
	$ogo = new-object management.objectgetoptions
	$proc = new-object management.managementclass $scope,$mp,$ogo
	$procID = ($proc.Create($cmd)).ProcessID
	return $procID
}

Have you ever been working in a Powershell console and have a command run longer than expected? Did you wish that you had wrapped that command in a Measure-Command so that you could view execution time? This has happened to me several times, so recently I started working on a Measure-HistoricalCommand function that would use Get-History to create a New-TimeSpan from the StartExecutionTime and EndExecutionTime properties. I would like to say thanks to @mtboren from vnugglets.com who helped add some functionality and speed up this function.

Function Measure-HistoricalCommand {
	param(
		## for getting info about the last X commands
		[parameter(Mandatory=$false,ParameterSetName="ByCommandCount")][alias("Count")][Int]$Last=1,
		## for getting info about a specific command ID
		[parameter(Mandatory=$true,ParameterSetName="ByCommandId")][alias("Id")][Int]$CommandID
	) ## end param

	process {
		## create the Get-History command expression to invoke; use -Id or -Count based on the params passed to this function
		$strGetHistoryExpr = "Get-History " + $(if ($CommandID) {"-Id $CommandID"} else {"-Count $Last"})
		Invoke-Expression $strGetHistoryExpr | %{
			$ts = New-TimeSpan -Start $_.StartExecutionTime -End $_.EndExecutionTime
			## again, take out the array, just return the object straight away
			#$myResults += New-Object PSObject -Property @{
			New-Object -TypeName PSObject -Property @{
				ID = $_.ID
				CommandLine = $_.CommandLIne
				EndExectuionTime = $_.EndExecutionTime
				StartExecutionTime = $_.StartExecutionTime
				TimeSpan = $ts
				TotalSec = $ts.TotalSeconds
			} ## end new-psobject
		} ## end History foreach-object
	} ## end process
} ## end fn