Demystifying Error Handling

by Oct 19, 2017

Any error in PowerShell code surfaces as an error record object. Check out the function below which extracts all relevant error information from such error record:

function Get-ErrorInfo

    $info = [PSCustomObject]@{
      Exception = $errorRecord.Exception.Message
      Reason    = $errorRecord.CategoryInfo.Reason
      Target    = $errorRecord.CategoryInfo.TargetName
      Script    = $errorRecord.InvocationInfo.ScriptName
      Line      = $errorRecord.InvocationInfo.ScriptLineNumber
      Column    = $errorRecord.InvocationInfo.OffsetInLine
      Date      = Get-Date
      User      = $env:username

This function makes error handling code a lot shorter and easier to understand. If you must respond immediately to an error, use the try/catch concept, and make sure you instruct cmdlets via -ErrorAction Stop to immediately stop when an error occurs:

    Stop-Service -Name someservice -ErrorAction Stop
    $_ | Get-ErrorInfo

If you want the code to complete, and only later check for errors that may have occurred, use -ErrorAction SilentlyContinue in conjunction with -ErrorVariable. Again, the function Get-ErrorInfo helps a lot:

$result = Get-ChildItem -Path C:\Windows -Filter *.ps1 -Recurse -ErrorAction SilentlyContinue -ErrorVariable myErrors
$myErrors | Get-ErrorInfo

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