What can I do with it?

PowerShell 2.0 introduces the concept of modules; essentially they are the evolution of snapins from PowerShell 1.0. Export-ModuleMember specifies elements from a module, like functions or variables, which can be exported. Note: This cmdlet can only be used within a *.psm1 script module file or a dynamic module created with New-Module.

Examples:

Create a new dynamic module using New-Module containing two variables inside the scriptblock. Export only the variable $s2 so that it is available for use. Note: Export-ModuleMember needs to be included inside the scriptblock.

New-Module -ScriptBlock {$s1 = 'Server1'; $s2 = 'Server2';
 Export-ModuleMember -Variable s2}

You will notice that $s1 is not available in the current session, but $s2 is.

The other area to use this cmdlet is within a *.psm1 script module file.  In the below example by default all functions would be exported if the Export-ModuleMember cmdlet was not used. However, by using the Export-ModuleMember cmdlet we can control which functions are exported and also export aliases.

So in the example below the Write-Logfile and Greet-User functions would be exported, but the Yesterdays-Date function would not. In addition the gu alias would be exported.

How could I have done this in PowerShell 1.0?

This functionality was not avaliable with snapins in PowerShell 1.0

1000 things 1% better

What can I do with it?

PowerShell 2.0 introduces the concept of modules; essentially they are the evolution of snapins from PowerShell 1.0. New-Module enables you to create a dynamic module from a script block that is available in the current session.

Note: New-Module does not create a module on disk available for use at a later date! However, Jeffrey Snover has created a module which will create a template for a new module on disk for you.

Examples:

Create a new dynamic module with the Function Write-Logfile as the scriptblock to create the module. Test to see whether the function is available from Get-Module or Get-Command.

New-Module -ScriptBlock
{Function Write-Logfile ($log) {$Logfile = "C:\Log.txt"; $log
| Out-File -FilePath $Logfile -Append}}
Get-Module
Get-Command Write-Logfile

You will see that Get-Module is not aware of the new module, but Get-Command is aware of the Write-Logfile function.

Create a new dynamic module with the Function Write-Logfile as the scriptblock to create the module. Give it a name and use Import-Module to make it available to Get-Module.   Test to see whether the function is available from Get-Module or Get-Command.

New-Module -ScriptBlock
{Function Write-Logfile ($log) {$Logfile = "C:\Log.txt"; $log
| Out-File -FilePath $Logfile -Append}} -Name LogfileModule
| Import-Module
Get-Module
Get-Command Write-Logfile

You will see that this time both Get-Module and Get-Command are aware of the LogfileModule and Write-Logfile function.

How could I have done this in PowerShell 1.0?

You could have created a custom snapin and imported with the Add-PSSnapin cmdlet.

1000 things 1% better!

They arrived just in time because I am currently preparing for a round of ESX patching and I needed to provide a report of hotfixes I was intending to deploy for a particular version of ESX. In the Update Manager GUI I had already created my baseline and scanned it against a host to produce a compliance report of hotfixes we would need to deploy this time.

You can see below that it produces a nice report for me, but I needed to export that information to a format whereby I can give that information to someone else.

One of the new cmdlets is Get-Baseline. I pointed this at my test baseline and with the code below was quickly able to get the information I needed out into a CSV file. I knew from the above report that I just needed to select any patches since 29/12/2009. One of the properties of the patches returned by Get-Baseline is the date it was published so first of all I set a date for which I could query after and stored it in the $BeginDate variable, I then queried the baseline using that date as a starting point.

$BeginDate = (Get-Date).adddays(-65)
Get-Baseline Test | Select-Object -ExpandProperty currentpatches
| Where-Object {$_.'releasedate' -gt $BeginDate}
| Select-Object Name,IDByVendor,Description,@{n='Product';e={$_.product | Select-Object -expandproperty Version}},ReleaseDate
| Export-Csv patches.csv -NoTypeInformation

Which produces an output like this:

You’ll notice that I make use of the ExpandProperty parameter for Select-Object which makes it nice and easy to get to properties which are returned in an array, otherwise although they look fine in the console, when you export them to CSV you will not get what you hope for.

It’s days like today when I’m especially glad I started using PowerShell and very thankful that the vendors of technologies I’m using make this stuff so simple by providing cmdlets for managing their products.

What can I do with it?

PowerShell 2.0 introduces the concept of modules; essentially they are the evolution of snapins from PowerShell 1.0. Import-Module enables you to add one or more modules to your current session.

Examples:

Import the PSDiagnostics module and examine the newly available commands in the session from that module by using Get-Module.

Import-Module PSDiagnostics
Get-Command -Module PSDiagnostics

You will see there are ten new functions available from that module.

Import only two functions, Start-Trace and Stop-Trace from the PSDiagnostics module and examine the newly available commands in the session from that module by using Get-Module.

Import-Module PSDiagnostics -Function Start-Trace,Stop-Trace
Get-Command -Module PSDiagnostics

You will see that this time only those two functions are available.

How could I have done this in PowerShell 1.0?

You could have used the Add-PSSnapin cmdlet to import custom snapins typically produced by third-parties. For example to import the popular Quest AD cmdlets snapin you would use the below:

Add-PSSnapin Quest.ActiveRoles.ADManagement

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What can I do with it?

Retrieve items from Event Logs including event logs generated by the Windows Event Log technology, new since Windows Vista / 2008 Server, in addition to the classic System, Security and Application Logs. Note: it requires .NET Framework 3.5 or later installed.

Examples:

Retrieve events from the Setup Event Log.

Get-WinEvent -LogName Setup

You’ll see the typical information you would normally view in Event Viewer.

Get-WinEvent includes a -FilterHashTable parameter which allows you to filter results at source rather than pulling back all the events and then piping them through to Where-Object to perform filtering, so much more effiicient.

Retrieve events from the System Event Log only where the Event ID is 10148.

Get-WinEvent -FilterHashtable @{Logname='System';ID=10148}

You will see that only the events with ID 10148 are returned.

How could I have done this in PowerShell 1.0?

You could have used the Get-EventLog cmdlet, however it is not able to retrieve information from event logs generated by the Windows Event Log technology such as the Setup log mentioned in the above examples.

Get-EventLog -LogName System | Where-Object {$_.EventID -eq 10148}

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What can I do with it?

Open Event Viewer on a local or remote computer.

Example:

Open Event Viewer on the remote computer Test01.

Show-EventLog -ComputerName Test01

You will see that Event Viewer on the remote computer Test01 opens on the local machine.

How could I have done this in PowerShell 1.0?

You could have typed the executable Eventvwr to open Event Viewer on a local computer. To view it on the remote computer Test01 use:

eventvwr \\Test01

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What can I do with it?

Remove an Event Log.

Example:

Remove the Event Log named App1 on the remote computer Test01. Confirm it has been removed with Get-EventLog.

Remove-EventLog -LogName App1 -ComputerName Test01
Get-EventLog -List -ComputerName Test01

Confirmation that the App1 Event Log has been removed.

Note: To perform this task remotely you will need to ensure that Remote Event Log Management has been added as an Exception in Windows Firewall.

How could I have done this in PowerShell 1.0?

You could have have used the .NET System.Diagnostics.Eventlog class and the Delete method to delete an event log.

[system.diagnostics.eventlog]::Delete("App1")

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Using Get-Stat, mem.usage.average comes back at 0% where it should be a significant value:

The same in the GUI, the other cluster memory stats have significant values, but Memory Usage Average flatlines along the bottom of the graph:

This stat shows normal behaviour against host machines. I reported it to VMware who confirmed it to be a bug in 4.0 U1.

Thought I would share in case anyone else spends some time scratching their head and checking maths in scripts like I did. I’ll post back when there is a fix.

What can I do with it?

Set the size and age properties of an Event Log.

Example:

Set the following properties on the Application Log on the remote computer Test01:

Maximum Size = 5MB

OverflowAction = DoNotOverWrite

Limit-EventLog -ComputerName Test01 -LogName Application 
-MaximumSize 5MB -OverflowAction DoNotOverWrite

Before:

After:

How could I have done this in PowerShell 1.0?

You could use WMI to set properties on an event log. For example to set the MaxFileSize of the Application Log to 5MB use the below. (Thanks to Richard Siddaway for the tip that you need to use psbase to save the changes, just Put() doesn’t work.)

$EventLog = Get-WmiObject -Class Win32_NTEventLogFile 
-Filter "LogFileName = 'Application'"
$EventLog.MaxFileSize = 5242880
$EventLog.psbase.Put()

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What can I do with it?

Create a custom Event Log.

Example:

Create a custom Event Log named App1 with an event source of AppEvent. Use the Get-EventLog cmdlet to confirm it has been created. Tip: New-EventLog requires a PowerShell session with elevated privileges.

New-EventLog -LogName App1 -Source AppEvent
Get-EventLog -List

You can see that the App1 Event Log has been created.

You can create entries in this log using the Write-EventLog cmdlet, e.g.

Write-EventLog -LogName App1 -Source AppEvent -ID 1020
-Message "Error 1020 has occured"

Here’s confirmation in Event Viewer that the App1 Event Log exists and we have created the above entry in it.

How could I have done this in PowerShell 1.0?

You could have used the .NET System.Diagnostics.EventLog class and the CreateEventSource method to create a custom event log.

$LogDetails = 
New-Object System.Diagnostics.EventSourceCreationData "AppEvent", "App1"
[System.Diagnostics.EventLog]::CreateEventSource($LogDetails)

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