Error Handling Powershell Example
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being able to handle errors helps to ensure that an unexpected event will not go on to wreck the system you are working on. Take the example below. Every week in our
Error Handling Powershell Try Catch
sample company (MyCompany.Com) Human Resources are going to upload a list telling us who error handling in powershell script should have access to the Expenses database. If a name isn’t in the list from HR we’re going to remove it
Powershell Error Handling Best Practices
from the group and that user will no longer be able to log expense claims: $AuthorizedUsers= Get-Content \\ FileServer\HRShare\UserList.txt $CurrentUsers=Get-ADGroupMember "Expenses Claimants" Foreach($User in $CurrentUsers) { If($AuthorizedUsers -notcontains $User) { Remove-ADGroupMember -Identity "Expenses Claimants" -User powershell error handling function $User } } Now, you can see where this is going to go wrong. One week HR doesn’t get around to uploading the list or, just as we are about to access the list, the file server dies. Suddenly PowerShell throws an error on the Get-Content cmdlet and the $AuthorizedUser variable remains empty. Because our script doesn’t handle errors, it continues to run and, in a very short space of time, powershell error handling silentlycontinue it has removed every user from our expenses group. Pretty soon the irate phone calls start flooding in and life gets a little less happy. The way to avoid all this is to catch the errors and then handle the event that caused them (which in this case is halt the script and have a shout at someone in HR). Terminating and Non-Terminating Errors One of the key things to know when catching errors is that only certain errors can be caught by default. Errors come in two types – terminating and non-terminating. A terminating error is an error that will halt a function or operation. If you make a syntax error or run out of memory, that is a terminating error. Terminating errors can be caught and handled. Non-terminating errors allow Powershell to continue and usually come from cmdlets or other managed situations. Under normal circumstances they cannot be caught by Try-Catch-Finally. The Get-Content error in the example above is a non-terminating error. Treating Non-Terminating Errors as Terminating So how do you catch a Non-Terminating error? Basically, you tell PowerShell to treat it as terminating. To do this you use the ErrorAction parameter. Every PowerShell cmdlet supports ErrorAction. By specifying -ErrorAction Stop on the end of a cmdlet
Keith BabinecJune 9, 201320 0 0 0 Today’s post (and this blog's inaugural post!) is An Introduction to Error Handling in PowerShell. We will discuss error types, the $error variable, error action preferences,
Powershell Error Handling Copy-item
try/catch blocks, and $lastexitcode. The first requirement is to understand the types of powershell error handling the rpc server is unavailable errors that can occur during execution. Terminating vs. Non-Terminating Errors: Terminating Error: A serious error during execution that halts the command
Powershell Error Handling Non-terminating
(or script execution) completely. Examples can include non-existent cmdlets, syntax errors that would prevent a cmdlet from running, or other fatal errors. Non-Terminating Error: A non-serious error that allows execution to continue despite the http://www.vexasoft.com/blogs/powershell/7255220-powershell-tutorial-try-catch-finally-and-error-handling-in-powershell failure. Examples include operational errors such file not found, permissions problems, etc. Update 12/13/2013: Writing a cmdlet? For further information regarding how a cmdlet should determine when to throw a terminating error or non-terminating error, MSDN has a niceexplanationhere. Update 12/13/2013: Want to know if an error you encountered is terminating or non-terminating? Check to see ifthe error behavioris affected by changing the$ErrorActionPreference. According to the MSDN documentation https://blogs.msdn.microsoft.com/kebab/2013/06/09/an-introduction-to-error-handling-in-powershell/ here, "Neither $ErrorActionPreference nor the ErrorAction common parameter affect how Windows PowerShell responds to terminating errors (those that stop cmdlet processing).". The $error variable: When either type of error occurs during execution, it is logged to a global variable called $error. This variable is a collection of PowerShell Error Objects with the most recent error at index 0. On a freshly initialized PowerShell instance (no errors have occurred yet) the $error variable is ready and waiting as an empty collection: PS C:\> $error.GetType() IsPublic IsSerial NameBaseType ----- ----- -------- TrueTrueArrayListSystem.Object PS C:\> $error.Count 0 In the next snippet I have executed a cmdlet that doesn’t exist, throwing an error. If we grab the count on $error, you will notice it has increased to one item. Dumping that object to the pipeline by accessing $error[0] just prints the error we already saw, right back at us. PS C:\> ThisCmdlet-DoesNotExist The term ‘ThisCmdlet-DoesNotExist' is not recognized as the name of a cmdlet, f unction, script file, or operable program. Check the spelling of the name, or i f a path was included, verify that the path is correct and try again. At line:1 char:24 + ThisCmdlet-DoesNotExist <<<< + CategoryInfo: ObjectNotFound: (ThisCmdlet-DoesNotExis
Steps (4 total) 1 Writing a Try Catch block The try catch block is written below. Place the code you want to execute in the try section. https://community.spiceworks.com/how_to/121063-using-try-catch-powershell-error-handling This will be ran first, then you can use the catch blow to get errors and take actions on those errors. Try { #Do some stuff } Catch { #Got an error http://sqlmag.com/powershell/handling-errors-powershell do something else } 2 Simple Get-ADuser Try Catch example $Users = Get-Content C:\temp\usersimport.txt foreach ($User in $Users) { try { Get-ADUser -Identity $User | Out-Null Write-Output "$user exists" } catch { error handling write-output "$User doesn't exist" } } 3 Getting error exceptions for catching specific errors. First you must generate the error you want to catch. For example query a user you know doesn't exists and then execute this line of code. $Error[0] | fl * -Force PowerShell stores all error data in $Error so we can get the contents of it. Gain we are after the powershell error handling exception code, which is highlighted in yellow. $Error[0] | fl * -Force 4 Add exceptions to catch statements We will now add a catch with the exception to catch only that error and do something special. $Users = Get-Content C:\temp\usersimport.txt foreach ($User in $Users) { try { Get-ADUser -Identity $User | Out-Null Write-Output "$user exists" } catch [Microsoft.ActiveDirectory.Management.ADIdentityNotFoundException]{ Write-Host "$User doesn't exist" -ForegroundColor Red } catch { Write-Output "Something else bad happend" } } Conclusion Use this instead of several if else statements and catch specific errors to aid in error handling. References Hey, Scripting Guy! Blog 8 Comments Mace Bryce Katz Jul 13, 2015 at 01:56pm Nicely done! I've wondered about the specific syntax of TRY ... CATCH for a while. Chipotle NetTechMike Jul 13, 2015 at 06:43pm This is fantastic. I wish Microsoft used this method of error handling when they create scripts in System Center. Serrano Tyler9771 Jul 13, 2015 at 07:04pm This is neat, I will have to try it out the next time I attempt some PowerShell Scriptin' Cayenne MerlinYoda Jul 13, 2015 at 09:30pm Nice write-up. Short and sweet. I haven't looked into PowerShell muc
Server 2016 SQL Server 2014 SQL Server 2012 SQL Server 2008 AdministrationBackup and Recovery Cloud High Availability Performance Tuning PowerShell Security Storage Virtualization DevelopmentASP.NET Entity Framework T-SQL Visual Studio Business IntelligencePower BI SQL Server Analysis Services SQL Server Integration Services SQL Server Reporting Services InfoCenters Advertisement Home > Database Administration > PowerShell > Handling Errors in PowerShell Handling Errors in PowerShell Mar 24, 2014 Allen White EMAIL Tweet Comments 0 Advertisement As DBAs, we're always working on protecting ourselves from problems by disaster recovery procedures like backups, but in our haste to get a script done, we also are prone to forget the same concept within our code to protect the process from errors. PowerShell provides ways to manage those times when there are errors in the execution of our script so we can recover, and still get the job done. Trap Statement for Handling Errors PowerShell 1.0 supported the Trap statement for handling errors, and I still frequently use that in my scripts. PowerShell works within the .NET Framework, so errors have multiple levels. It's rare that the top level error message PowerShell returns will help you solve the problem. Let's take, for example. the case where we want to use the SMO CheckTables('FAST') method, which effectively runs DBCC CHECKDB(N'AdventureWorks', REPAIR_FAST). If we run call this method without error handling, we'll get this message. Exception calling "CheckTables with "1" argument(s): "Check tables failed for Database 'AdventureWorks'." Now, that isn't very helpful at all. Here's the Trap function I frequently use. # Handle any errors that occur Trap { # Handle the error $err = $_.Exception write-output $err.Message while( $err.InnerException ) { $err = $err.InnerException write-output $err.Message }; # End the script. break } When the CheckTables('FAST') method is called, now I get