Try catch does not seem to have an effect

Question

I am new to powershell  and I am trying to add error handling via try catch statements  but they don t seem to actually be catching the error  This is powershell v2 CP3    objComputer    objResult Properties   strComputerName    objComputer name write-host  Checking machine     strComputerName  try        colItems   get-wmiobject -class  Win32 PhysicalMemory  -namespace  root CIMV2  -computername  strComputerName -Credential  credentials     foreach   objItem in  colItems                 write-host  Bank Label     objItem BankLabel         write-host  Capacity      objItem Capacity   1024   1024          write-host  Caption     objItem Caption         write-host  Creation Class Name     objItem CreationClassName               write-host         Catch        write-host  Failed to get data from machine  Error       Exception Message         write-host   finally          When it fails to contact a specific machine  I get this in console  and not my clean catch message      Get-WmiObject   The RPC server is   unavailable   Exception from HRESULT    0x800706BA  At Z  7 0 Intern   Programvare Powershell Get memory of   all computers in AD ps1 25 char 34              colItems   get-wmiobject  lt  lt  lt  lt   -class  Win32 PhysicalMemory    -namespace  root CIMV2  -computername  strComputerName -Credential    credentials         CategoryInfo            InvalidOperation       Get-WmiObject     COMException         FullyQualifiedErrorId     GetWMICOMException Microsoft PowerShell Commands GetWmiObjectCommand

User · Answer

It is also possible to set the error action preference on individual cmdlets, not just for the whole script. This is done using the parameter ErrorAction (alisa EA) which is available on all cmdlets.

Example

try 
{
 Write-Host $ErrorActionPreference; #Check setting for ErrorAction - the default is normally Continue
 get-item filethatdoesntexist; # Normally generates non-terminating exception so not caught
 write-host "You will hit me as exception from line above is non-terminating";  
 get-item filethatdoesntexist -ErrorAction Stop; #Now ErrorAction parameter with value Stop causes exception to be caught 
 write-host "you won't reach me as exception is now caught";
}
catch
{
 Write-Host "Caught the exception";
 Write-Host $Error[0].Exception;
}

User · Answer

In my case  it was because I was only catching specific types of exceptions   try         get-item -Force -LiteralPath  Path -ErrorAction Stop       if file exists     if   Path -like          fileType    n     Network     elseif   Path -like           fileType    l    Local     else   fileType    u    Unknown File Type      catch  System UnauthorizedAccessException    fileType    i    Inaccessible catch  System Management Automation ItemNotFoundException   fileType    x    Doesn t Exist   Added these to handle additional the exception causing the terminating error  as well as unexpected exceptions  catch  System Management Automation DriveNotFoundException   fileType    x    Doesn t Exist catch   fileType  u    Unknown

User · Answer

I was able to duplicate your result when trying to run a remote WMI query   The exception thrown is not caught by the Try Catch  nor will a Trap catch it  since it is not a  terminating error    In PowerShell  there are terminating errors and non-terminating errors    It appears that Try Catch Finally and Trap only works with terminating errors   It is logged to the  error automatic variable and you can test for these type of non-terminating errors by looking at the    automatic variable  which will let you know if the last operation succeeded   true  or failed   false    From the appearance of the error generated  it appears that the error is returned and not wrapped in a catchable exception   Below is a trace of the error generated   PS C  scripts PowerShell gt  Trace-Command -Name errorrecord  -Expression  Get-WmiObject win32 bios -ComputerName HostThatIsNotThere   -PSHost DEBUG  InternalCommand Information  0    Constructor Enter Ctor Microsoft PowerShell Commands GetWmiObjectCommand  25857563 DEBUG  InternalCommand Information  0    Constructor Leave Ctor Microsoft PowerShell Commands GetWmiObjectCommand  25857563 DEBUG  ErrorRecord Information  0    Constructor Enter Ctor System Management Automation ErrorRecord  19621801 exception   System Runtime InteropServices COMException  0x800706BA   The RPC server is unavailable   Exception from HRESULT  0x800706BA     at System Runtime InteropServices Marshal ThrowExceptionForHRInternal Int32 errorCode  IntPtr errorInfo     at System Management ManagementScope InitializeGuts Object o     at System Management ManagementScope Initialize      at System Management ManagementObjectSearcher Initialize      at System Management ManagementObjectSearcher Get      at Microsoft PowerShell Commands GetWmiObjectCommand BeginProcessing   errorId   GetWMICOMException errorCategory   InvalidOperation targetObject   DEBUG  ErrorRecord Information  0    Constructor Leave Ctor System Management Automation ErrorRecord  19621801   A work around for your code could be   try        colItems   get-wmiobject -class  Win32 PhysicalMemory  -namespace  root CIMV2  -computername  strComputerName -Credential  credentials     if                  foreach   objItem in  colItems                     write-host  Bank Label     objItem BankLabel           write-host  Capacity      objItem Capacity   1024   1024            write-host  Caption     objItem Caption           write-host  Creation Class Name     objItem CreationClassName                 write-host                   else              throw  error 0  Exception

User · Answer

This is my solution  When Set-Location fails it throws a non-terminating error which is not seen by the catch block  Adding -ErrorAction Stop is the easiest way around this   try       Set-Location   YourPath  -ErrorAction Stop    catch       Write-Host  Exception has been caught

User · Answer

Adding  -EA Stop  solved this for me

User · Answer

If you want try catch to work for all errors  not just the terminating errors  you can manually make all errors terminating by setting the ErrorActionPreference    try        ErrorActionPreference    Stop    Make all errors terminating    get-item filethatdoesntexist    normally non-terminating    write-host  You won t hit me       catch     Write-Host  Caught the exception      Write-Host  Error 0  Exception   finally      ErrorActionPreference    Continue    Reset the error action pref to default     Alternatively    you can make your own trycatch function that accepts scriptblocks so that your try catch calls are not as kludge  I have mine return true false just in case i need to check if there was an error    but it doesnt have to  Also  exception logging is optional  and can be taken care of in the catch  but i found myself always calling the logging function in the catch block  so i added it to the try catch function   function log  System String   text  write-host  text    function logException      log  Logging current exception        log  Error 0  Exception      function mytrycatch   System Management Automation ScriptBlock   try                       System Management Automation ScriptBlock   catch                       System Management Automation ScriptBlock    finally                Make all errors terminating exceptions       ErrorActionPreference    Stop          Set the trap     trap  System Exception             Log the exception          logException             Execute the catch statement          amp   catch             Execute the finally statement          amp   finally            There was an exception  return false         return  false               Execute the scriptblock      amp   try         Execute the finally statement      amp   finally        The following statement was hit   so there were no errors with the scriptblock     return  true       execute your own try catch mytrycatch           gi filethatdoesnotexist   normally non-terminating         write-host  You won t hit me                   Write-Host  Caught the exception

User · Answer

Edit  As stated in the comments  the following solution applies to PowerShell V1 only   See this blog post on  Technical Adventures of Adam Weigert  for details on how to implement this   Example usage  copy paste from Adam Weigert s blog    Try       echo     Do some work         echo     Try divide by zero    0 0     -Catch       echo      Cannot handle the error  will rethrow            throw      -Finally       echo     Cleanup resources         Otherwise you ll have to use exception trapping

[powershell] Try/catch does not seem to have an effect

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