Dittenhafer.Net

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Posted by: Dan Dittenhafer	5/2/2011
For the last couple of weeks I have been required to import a data log file (CSV) from a legacy SCADA system into my centralized data management system. It occured to me today that I might be able to use PowerShell to automate some of the importing steps which include import to a DEV, QA and Production system. I'm still working on this script, but in the process of developing it, I had a need to learn more about an exception that was occuring in the script. I had my try/catch block already specified, but was simply using Write-Error, as in the following code sample, to report a generic message "Failed to..." whenever the catch block was executed. try { $session = Logon... } catch { Write-Error "Failed to logon to DMS." } I searched the local PowerShell help and didn't see any info on how to get more detail about a given exception. I searched a little online including about_Try_Catch_Finally and didn't find any gems. Then I thought "Maybe there is a global object, like `$host`, that as some error info". I tried $Err and $Error with no success... then I tried `$_` and surprise! It resulted in an object with exception details! See the code sample below, where the `$_` object is used in the catch block and converted to a string for output to the Write-Error stream. try { $session = Logon... } catch { # Using $_ in the catch block to include more details about the error that occured. Write-Error ("Failed to logon to DMS." + $_) } When run through Get-Member, the $_ object in the catch block returns the following result: TypeName: System.Management.Automation.ErrorRecord Name MemberType Definition ---- ---------- ---------- Equals Method bool Equals(System.Object obj) GetHashCode Method int GetHashCode() GetObjectData Method System.Void GetObjectData(System.Runtime.Serialization.SerializationInfo info, System.Runtime.Serialization.StreamingContext context) GetType Method type GetType() ToString Method string ToString() CategoryInfo Property System.Management.Automation.ErrorCategoryInfo CategoryInfo {get;} ErrorDetails Property System.Management.Automation.ErrorDetails ErrorDetails {get;set;} Exception Property System.Exception Exception {get;} FullyQualifiedErrorId Property System.String FullyQualifiedErrorId {get;} InvocationInfo Property System.Management.Automation.InvocationInfo InvocationInfo {get;} PipelineIterationInfo Property System.Collections.ObjectModel.ReadOnlyCollection`1[[System.Int32, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]] PipelineIterationInfo {get;} TargetObject Property System.Object TargetObject {get;} PSMessageDetails ScriptProperty System.Object PSMessageDetails {get=& { Set-StrictMode -Version 1; $this.Exception.InnerException.PSMessageDetails };} Of course, after having figured this out, I thought "Hmm... I bet others might have the same question about getting more exception detail inside a catch block", and so was born this blog entry. Hope it helps!

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