Ezine 209 PowerShell -ErrorAction SilentlyContinue

PowerShell -ErrorAction SilentlyContinue

If a PowerShell script halts, or a portion of the code does not work, what would you like to happen next?  One popular solution is to tell the script to silently continue.

Windows PowerShell -ErrorAction SilentlyContinue


-ErrorAction Example:  Check If a Service Has Been Installed

# PowerShell -ErrorAction SilentlyContinue example
$SrvName = "Printer Spooler"
$Service = Get-Service -display $SrvName -ErrorAction SilentlyContinue
if (-not $Service) {$SrvName + " is NOT installed, check the name."}
else {$SrvName + " is installed."
$SrvName + "’s status is: " + $service.Status }

Note 1:   While this example shows -ErrorAction, you must decide if it’s better than the built-in message ObjectNotFound.  Action Point remove -ErrorAction SilentlyContinue from the above script.

Note 2:  The actual name of this service is Print Spooler (not Printer).  I made this deliberate mistake so as to create the error message.

Problems With Stop-Process

Take the scenario where you create a PowerShell script which is designed to kill several processes.  The problem arises when the first process does not exist, consequently the script comes to a halt prematurely.

"Cannot find a process with the process identifier 51322"

Zapping processes is a classic job for SilentlyContinue … provided you know what you’re doing!  If you would like to try this for real, then launch Task Manager and note the PID (process ID) of one real and two fictitious processes.   Then substitute your PIDs for 5132, 5075, 5072 in my script below.

# PowerShell SilentlyContinue
Stop-Process 5132, 5075, 5072 -ErrorAction SilentlyContinue

Note 3:  Please don’t use Stop-Process unless you understand what you are doing, for instance, you make a ‘walk-though’ of stopping the process with task manager.

Problems Displaying Registry Hives

One common problem when enumerating hives in the registry is that the permissions on the security hive cause an error in the PowerShell script.

# PowerShell Registry Listing
Set-Location HKLM:\
Get-Childitem -ErrorAction SilentlyContinue

Note 4: -ErrorAction SilentlyContinue suppresses the error message PermissionDenied to the SECURITY hive.

Note 5:  In the output ‘SKC’ means SubKey count and ‘VC’ means Value count.

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For Mr Organized there is a nifty subnet calculator, you enter the network address and the subnet mask, then IPAT works out the usable addresses and their ranges. 

For Mr Lazy IPAT discovers and then displays the IP addresses of existing computers. Download the Free IP Address Tracker

More PowerShell Problems -ErrorAction Solutions

Problem: finding files in the System32 folder using a ‘where .extension’ clause.  Specifically, I got this error:
Access to the path ‘C:\Windows\System32\LogFiles\WMI\RtBackup’ is denied.

Solution: add -ErrorAction SilentlyContinue after -recurse.

# PowerShell example: Find executables under the System32 folder
$Path = "C:\Windows\System32"
Get-ChildItem $Path -recurse -ErrorAction SilentlyContinue `
| where {$_.extension -match "exe"}

Note 6:  My friend ‘Mad’ Mick says you can cure the problem by simply saying:
Get-ChildItem C:\Windows\System32\*.exe -recurse

Guy responds:  It’s true that Mick’s method is superior, but I wanted a simple problem that -ErrorAction could cure.

Research -ErrorAction

# Research PowerShell SilentlyContinue
Get-Help about_commonParameters

Note 7:  Incidentally, Help about_common* works just as well.

Note 8:  Other scripts may benefit from substituting Stop or Inquire for the action to SilentlyContinue.

-ErrorAction Abbreviations or Aliases

Instead of ErrorAction SilentlyContinue you can try : -EA 0

# PowerShell Registry Listing
Set-Location HKLM:\
Get-Childitem -EA 0

Researching the about_commonParameters file help file will explain why these also work:
-EA 1 Continue
-EA 2 Inquire
-EA 3 Confirm
-EA 4 Stop

Guy Recommends: Tools4ever’s UMRAUMRA The User Management Resource Administrator

Tired of writing scripts? The User Management Resource Administrator solution by Tools4ever offers an alternative to time-consuming manual processes.

It features 100% auto provisioning, Helpdesk Delegation, Connectors to more than 130 systems/applications, Workflow Management, Self Service and many other benefits. Click on the link for more information onUMRA.

Summary of PowerShell -ErrorAction

If a script pauses to produce an error message there maybe times when you want to suppress such system messages.  Alternatively, you may want -ErrorAction to stop the script.

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See more Windows PowerShell examples

PowerShell Home   • Foreach loops   • PowerShell Foreach   • Foreach-Object cmdlet

Syntax   • Variables   • -whatIf   • -ErrorAction   • Windows 8 PowerShell   • Free CSV Import Tool

PowerShell Functions   • [System.Math]   • Get-Credential   • Windows PowerShell   • PowerShell 3.0

Please email me if you have a better example script.  Also please report any factual mistakes, grammatical errors or broken links, I will be happy to  correct the fault.