Creating Get-WinEvent queries with FilterHashtable

To read the original June 3, 2014 Scripting Guy blog post, see Use FilterHashTable to Filter Event Log with PowerShell.

This article is an excerpt of the original blog post and explains how to use the Get-WinEvent cmdlet's FilterHashtable parameter to filter event logs. PowerShell's Get-WinEvent cmdlet is a powerful method to filter Windows event and diagnostic logs. Performance improves when a Get-WinEvent query uses the FilterHashtable parameter.

When you work with large event logs, it's not efficient to send objects down the pipeline to a Where-Object command. Prior to PowerShell 6, the Get-EventLog cmdlet was another option to get log data. For example, the following commands are inefficient to filter the Microsoft-Windows-Defrag logs:

Get-EventLog -LogName Application | Where-Object Source -Match defrag

Get-WinEvent -LogName Application | Where-Object { $_.ProviderName -Match 'defrag' }

The following command uses a hash table that improves the performance:

Get-WinEvent -FilterHashtable @{
   LogName='Application'
   ProviderName='*defrag'
}

Blog posts about enumeration

This article presents information about how to use enumerated values in a hash table. For more information about enumeration, read these Scripting Guy blog posts. To create a function that returns the enumerated values, see Enumerations and Values. For more information, see the Scripting Guy series of blog posts about enumeration.

Hash table key/value pairs

To build efficient queries, use the Get-WinEvent cmdlet with the FilterHashtable parameter. FilterHashtable accepts a hash table as a filter to get specific information from Windows event logs. A hash table uses key/value pairs. For more information about hash tables, see about_Hash_Tables.

If the key/value pairs are on the same line, they must be separated by a semicolon. If each key/value pair is on a separate line, the semicolon isn't needed. For example, this article places key/value pairs on separate lines and doesn't use semicolons.

This sample uses several of the FilterHashtable parameter's key/value pairs. The completed query includes LogName, ProviderName, Keywords, ID, and Level.

The accepted key/value pairs are shown in the following table and are included in the documentation for the Get-WinEvent FilterHashtable parameter.

The following table displays the key names, data types, and whether wildcard characters are accepted for a data value.

Key name Value data type Accepts wildcard characters?
LogName <String[]> Yes
ProviderName <String[]> Yes
Path <String[]> No
Keywords <Long[]> No
ID <Int32[]> No
Level <Int32[]> No
StartTime <DateTime> No
EndTime <DateTime> No
UserID <SID> No
Data <String[]> No
* <String[]> No

Building a query with a hash table

To verify results and troubleshoot problems, it helps to build the hash table one key/value pair at a time. The query gets data from the Application log. The hash table is equivalent to Get-WinEvent –LogName Application.

To begin, create the Get-WinEvent query. Use the FilterHashtable parameter's key/value pair with the key, LogName, and the value, Application.

Get-WinEvent -FilterHashtable @{
   LogName='Application'
}

Continue to build the hash table with the ProviderName key. The ProviderName is the name that appears in the Source field in the Windows Event Viewer. For example, .NET Runtime in the following screenshot:

Image of Windows Event Viewer sources.

Update the hash table and include the key/value pair with the key, **ProviderName, and the value, .NET Runtime.

Get-WinEvent -FilterHashtable @{
   LogName='Application'
   ProviderName='.NET Runtime'
}

If your query needs to get data from archived event logs, use the Path key. The Path value specifies the full path to the log file. For more information, see the Scripting Guy blog post, Use PowerShell to Parse Saved Event Logs for Errors.

Using enumerated values in a hash table

Keywords is the next key in the hash table. The Keywords data type is an array of the [long] value type that holds a large number. Use the following command to find the maximum value of [long]:

[long]::MaxValue
9223372036854775807

For the Keywords key, PowerShell uses a number, not a string such as Security. Windows Event Viewer displays the Keywords as strings, but they are enumerated values. In the hash table, if you use the Keywords key with a string value, an error message is displayed.

Open the Windows Event Viewer and from the Actions pane, click on Filter current log. The Keywords drop-down menu displays the available keywords, as shown in the following screenshot:

Image of Windows Event Viewer keywords.

Use the following command to display the StandardEventKeywords property names.

[System.Diagnostics.Eventing.Reader.StandardEventKeywords] | Get-Member -Static -MemberType Property
   TypeName: System.Diagnostics.Eventing.Reader.StandardEventKeywords
Name             MemberType Definition
—-             ———- ———-
AuditFailure     Property   static System.Diagnostics.Eventing.Reader.StandardEventKey…
AuditSuccess     Property   static System.Diagnostics.Eventing.Reader.StandardEventKey…
CorrelationHint  Property   static System.Diagnostics.Eventing.Reader.StandardEventKey…
CorrelationHint2 Property   static System.Diagnostics.Eventing.Reader.StandardEventKey…
EventLogClassic  Property   static System.Diagnostics.Eventing.Reader.StandardEventKey…
None             Property   static System.Diagnostics.Eventing.Reader.StandardEventKey…
ResponseTime     Property   static System.Diagnostics.Eventing.Reader.StandardEventKey…
Sqm              Property   static System.Diagnostics.Eventing.Reader.StandardEventKey…
WdiContext       Property   static System.Diagnostics.Eventing.Reader.StandardEventKey…
WdiDiagnostic    Property   static System.Diagnostics.Eventing.Reader.StandardEventKey…

The enumerated values are documented in the .NET Framework. For more information, see StandardEventKeywords Enumeration.

The Keywords names and enumerated values are as follows:

Name Value
AuditFailure 4503599627370496
AuditSuccess 9007199254740992
CorrelationHint2 18014398509481984
EventLogClassic 36028797018963968
Sqm 2251799813685248
WdiDiagnostic 1125899906842624
WdiContext 562949953421312
ResponseTime 281474976710656
None 0

Update the hash table and include the key/value pair with the key, Keywords, and the EventLogClassic enumeration value, 36028797018963968.

Get-WinEvent -FilterHashtable @{
   LogName='Application'
   ProviderName='.NET Runtime'
   Keywords=36028797018963968
}

Keywords static property value (optional)

The Keywords key is enumerated, but you can use a static property name in the hash table query. Rather than using the returned string, the property name must be converted to a value with the Value__ property.

For example, the following script uses the Value__ property.

$C = [System.Diagnostics.Eventing.Reader.StandardEventKeywords]::EventLogClassic
Get-WinEvent -FilterHashtable @{
   LogName='Application'
   ProviderName='.NET Runtime'
   Keywords=$C.Value__
}

Filtering by Event Id

To get more specific data, the query's results are filtered by Event Id. The Event Id is referenced in the hash table as the key ID and the value is a specific Event Id. The Windows Event Viewer displays the Event Id. This example uses Event Id 1023.

Update the hash table and include the key/value pair with the key, ID and the value, 1023.

Get-WinEvent -FilterHashtable @{
   LogName='Application'
   ProviderName='.NET Runtime'
   Keywords=36028797018963968
   ID=1023
}

Filtering by Level

To further refine the results and include only events that are errors, use the Level key. Windows Event Viewer displays the Level as string values, but they are enumerated values. In the hash table, if you use the Level key with a string value, an error message is displayed.

Level has values such as Error, Warning, or Informational. Use the following command to display the StandardEventLevel property names.

[System.Diagnostics.Eventing.Reader.StandardEventLevel] | Get-Member -Static -MemberType Property
   TypeName: System.Diagnostics.Eventing.Reader.StandardEventLevel

Name          MemberType Definition
----          ---------- ----------
Critical      Property   static System.Diagnostics.Eventing.Reader.StandardEventLevel Critical {get;}
Error         Property   static System.Diagnostics.Eventing.Reader.StandardEventLevel Error {get;}
Informational Property   static System.Diagnostics.Eventing.Reader.StandardEventLevel Informational {get;}
LogAlways     Property   static System.Diagnostics.Eventing.Reader.StandardEventLevel LogAlways {get;}
Verbose       Property   static System.Diagnostics.Eventing.Reader.StandardEventLevel Verbose {get;}
Warning       Property   static System.Diagnostics.Eventing.Reader.StandardEventLevel Warning {get;}

The enumerated values are documented in the .NET Framework. For more information, see StandardEventLevel Enumeration.

The Level key's names and enumerated values are as follows:

Name Value
Verbose 5
Informational 4
Warning 3
Error 2
Critical 1
LogAlways 0

The hash table for the completed query includes the key, Level, and the value, 2.

Get-WinEvent -FilterHashtable @{
   LogName='Application'
   ProviderName='.NET Runtime'
   Keywords=36028797018963968
   ID=1023
   Level=2
}

Level static property in enumeration (optional)

The Level key is enumerated, but you can use a static property name in the hash table query. Rather than using the returned string, the property name must be converted to a value with the Value__ property.

For example, the following script uses the Value__ property.

$C = [System.Diagnostics.Eventing.Reader.StandardEventLevel]::Informational
Get-WinEvent -FilterHashtable @{
   LogName='Application'
   ProviderName='.NET Runtime'
   Keywords=36028797018963968
   ID=1023
   Level=$C.Value__
}