{"id":48,"date":"2019-07-01T16:19:45","date_gmt":"2019-07-01T16:19:45","guid":{"rendered":"https:\/\/www.practicalpowershell.com\/post\/conditional-variables"},"modified":"2020-03-09T18:17:10","modified_gmt":"2020-03-10T00:17:10","slug":"conditional-variables","status":"publish","type":"post","link":"https:\/\/practicalpowershell.com\/conditional-variables\/","title":{"rendered":"Conditional Variables"},"content":{"rendered":"

\"\"<\/a>Making decisions in PowerShell. In this weeks PowerShell tip of the week we will review ways we can use variables to help drive scripts conditionally. This means that when a variable it set to a certain value then a subsection code its either run or skipped. Thus we can use variables conditionally to make this happen.

\nExample 1<\/strong>

\nFor this sample code, a PowerShell query is made using CIMInstance and it fails, a good fallback is Get-WMIObject. We can use a combo of Try and Catch and a variable to store a result. The variable will be used to either trigger a WMI query (if the CIM query fails) or to ignore the WMI query if the CIM query worked as expected.

\nFirst section of code attempts to query a server via a CIM Instance. If the query failed (Inside the Try section) the code section in the Catch section will be run, and in this case it will set a $WMIQuery variable to $True:
\n[sourcecode language=”powershell”]
\nTry {
\n $MaximumSize = (Get-CimInstance -ComputerName $Server -Query "Select * from win32_PageFileSetting" -ErrorAction STOP| select-object MaximumSize).MaximumSize
\n} Catch {
\n $WMIQuery = $True
\n}
\n[\/sourcecode]
\nRight after that the CIM query section, we can check the $WMIQuery variable to see it is true. If the variable is true (which it would be if the CIM query fails), then this code is executed:
\n[sourcecode language=”powershell”]
\nIf ($WMIQuery) { <\/p>\n

Try {
\n $MaximumSize = (Get-WMIObject -ComputerName $Server -Class win32_PageFileSetting -ErrorAction STOP | select-object MaximumSize).MaximumSize
\n } Catch {
\n $MaximumSize = 'Managed'
\n }
\n}
\n[\/sourcecode]
\nConditional variables can be used to create a determined flow in a script as well as be a part of error handling (Try {} Catch{}).

\nExample 2<\/strong>

\nIn this next sample code block we will first set a variable ($Subscriptions) to $False. Then we will run a section of code to check to see if there are Edge Subscriptions (Edge Servers present in Exchange) and if the query fails, register this as no Edge subscriptions.
\n[sourcecode language=”powershell”]
\n$Subscriptions = $False Try { $EdgeSubscriptions = Get-EdgeSubscription -ErrorAction Stop | Select Name,Site,Domain,IsValid $Subscriptions = $True } Catch { $Line = 'No Edge Transport Servers or Subscriptions found.' | Out-File $Destination -Append }
\n[\/sourcecode]
\nIf the Get-EdgeSubscription succeeds and the $Subscriptions variable is changed from $False to $True. Once that variable set, we move on to another code section which will ONLY execute if the $Subscriptions variable is $True:
\n[sourcecode language=”powershell”]
\nIf ($Subscriptions) { (Code to run) }
\n[\/sourcecode]
\nThis last section of code could be written a couple of ways:
\n[sourcecode language=”powershell”]
\nIf ($Subscriptions) { }
\n[\/sourcecode]
\nOr
\n[sourcecode language=”powershell”]
\nIf ($Subscriptions -eq $True) {}
\n[\/sourcecode]
\nEither way, if the $Subscriptions variable is $True, the code section in the brackets ( { } ) will execute. Now, we can also execute code if a variable false:
\n[sourcecode language=”powershell”]
\nIf (!(Subscriptions) { }
\n[\/sourcecode]
\nOr
\n[sourcecode language=”powershell”]
\nIf ($Subscriptions -eq $False) {}
\n[\/sourcecode]
\n** NOTE ** <\/strong> One thing to be careful of is that some cmdlets may not fail and only return a Null result, which would defeat the purpose of the Try{} Catch{} error handling. In cases like that, we may want to have an IF () check to see if a variable is Null instead. Still conditional because we are looking for a value to determine a course of action.

\nExample 3 <\/strong>

\nIn this last example, we can execute a code block based on what version of Exchange (or Windows) is running on a server. The first code section will determine the value for the $ExVersion variable:
\n[sourcecode language=”powershell”]
\n$ExVersion = $Null
\nIf ($Version -like '*15.2*') {$ExVersion = '2019'}
\nIf ($Version -like '*15.1*') {$ExVersion = '2016'}
\nIf ($Version -like '*15.0*') {$ExVersion = '2013'}
\nIf ($Version -like '*14.*') {$ExVersion = '2010'}
\nIf ($Version -like '*8.*') {$ExVersion = '2007'}
\n[\/sourcecode]
\nOnce this variable is populated, we can then run a subset of code based on the value of the $ExVersion variable:
\n[sourcecode language=”powershell”]
\nIf ($ExVersion -eq 2019) { }
\nIf ($ExVersion -eq 2016) { }
\nIf ($ExVersion -eq 2013) { }
\n[\/sourcecode]
\nAs we can see by the above examples, using a variables value to determine the direction of the script and what code to execute can be useful in some scenarios.<\/p>\n","protected":false},"excerpt":{"rendered":"

Making decisions in PowerShell. In this weeks PowerShell tip of the week we will review ways we can use variables to help drive scripts conditionally. This means that when a variable it set to a certain value then a subsection code its either run or skipped. Thus we can use variables conditionally to make this […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"rop_custom_images_group":[],"rop_custom_messages_group":[],"rop_publish_now":"initial","rop_publish_now_accounts":[],"rop_publish_now_history":[],"rop_publish_now_status":"pending","_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[1],"tags":[],"class_list":["post-48","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"yoast_head":"\nConditional Variables - Practical PowerShell<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/practicalpowershell.com\/conditional-variables\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Conditional Variables - Practical PowerShell\" \/>\n<meta property=\"og:description\" content=\"Making decisions in PowerShell. 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