Piping powershell messages to Write-EventLog

Question

I have a powershell script that runs a custom cmdlet. It is run by Task Scheduler and I want to log what it does.

This is my current crude version:

Add-PsSnapIn MyCmdlets
Write-EventLog -LogName "Windows Powershell" -Source "Powershell" -Message "Starting Update-ClubNumbers" -EventId 0
Get-ClubMembers -HasTemporaryNumber -show all | Update-ClubNumbers -Verbose
Write-EventLog -LogName "Windows Powershell" -Source "Powershell" -Message "Finished Update-ClubNumbers" -EventId 0

What I would like to do is log the output of my custom cmdlet. Ideally I'd like to create different types of event log entries based on whether it was a warning or a verbose message.

Update: I don't want to log the return value of the commandlet. The Update-ClubMembers cmdlet does not return an object. I want to log any verbose messages written by WriteVerbose and I want to log errors created by ThrowTerminatingError.

vonPryz · Accepted Answer · 2011-06-28T05:46:40.387

1

What kind of data does the cmdlet return? You could save it into a string like so,

$ret = Get-ClubMembers -Whatever...
Write-EventLog -LogName "Windows Powershell" -Source "Powershell" -Message $ret -EventId 0

If the data returned is an array, you must create an ordinary string first. Othervise, the log message will just contain the array name. Maybe something like this

$ret = Get-ClubMembers -Whatever...
Write-EventLog -LogName "Windows Powershell" -Source "Powershell" -Message $($ret -join [Environment]::NewLine) -EventId 0

Ed:

As far as I know - and I'd really like to be wrong in this one - you have run into a nasty limitation of Powershell. Keith Hill's blog has kind of a work-around. You mentioned that the cmdlet is a custom one. Maybe you could ask its developer to add a switcht that toggles the messages to stdout, so that executing the cmdlet would return its output as an easily logged string array.

edited Jun 28 '11 at 05:46

answered Jun 27 '11 at 09:38

vonPryz

176
5

It doesn't return anything. It prints status messages with WriteVerbose and errors with ThrowTerminatingError. Those are the things I want to log. – Richard Jun 27 '11 at 12:39
Thanks for the edit. This does seem like a very nasty limitation. It seems like the easiest way to fix is to get the custom script to output a status object, but it seems messy. – Richard Jun 28 '11 at 08:24
Interesting. Looks like MS has relieved us of this limitation in PS 3.0. https://connect.microsoft.com/feedback/ViewFeedback.aspx?FeedbackID=297055&SiteID=99 – Dave Markle Jul 09 '13 at 14:58

score 0 · Answer 2 · answered Jun 28 '11 at 08:56

As pointed out by vonPryz there does seem to be no way of capturing verbose messages from a cmdlet, however ThrowTerminatingError throws an exception and I've found that you can capture those and log the error like this:

try
{
    Get-ClubMembers -HasTemporaryEbuNumber -show all | Update-EbuNumbers
}
catch [System.Exception]
{
    Write-EventLog -LogName "Windows Powershell" -Source "Powershell" -Message $_.Exception.ToString() -EventId 0 -EntryType Error
}

Piping powershell messages to Write-EventLog

2 Answers2