4 Extensions: finding and adding modules

Extensions: finding and adding modules



79



PS C:\> help *network*

Name

---Get-BCNetworkConfiguration

Get-DtcNetworkSetting

Set-DtcNetworkSetting

Get-SmbServerNetworkInterface

Get-SmbClientNetworkInterface



Category

-------Function

Function

Function

Function

Function



Module

-----BranchCache

MsDtc

MsDtc

SmbShare

SmbShare



As you can see, PowerShell discovered several commands (of the “function” variety)

that have the word “network” in their name. You could then ask for help on one of

these, even though you haven’t loaded the module:

PS C:\> help Get-SmbServerNetworkInterface

NAME

Get-SmbServerNetworkInterface

SYNTAX

Get-SmbServerNetworkInterface [-CimSession ]

[-ThrottleLimit ] [-AsJob] []



If you want to, you could even run the command, and PowerShell would make sure

the module was loaded for you. This auto-discovery and auto-loading functionality is



Figure 7.1



Changing the PSModulePath environment variable in Windows



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CHAPTER 7



Adding commands



quite useful, helping you to find and use commands that aren’t even present in the

shell when you start.

TIP You can also use Get-Module to retrieve a list of modules available on a

remote computer, and use Import-Module to load a remote module into your

current PowerShell session. You’ll learn how to do that in chapter 13 on

remote control.



PowerShell’s module auto-discovery enables the shell to complete command names

(using Tab in the console, or IntelliSense in the ISE), display help, and run commands, even for modules you haven’t explicitly loaded into memory. These features

make it worth the effort to keep PSModulePath complete and up to date.

What if a module isn’t located in one of the paths referenced by PSModulePath?

You would need to run Import-Module and specify the complete path to the module,

such as C:\MyPrograms\Something\MyModule.

If you have a Start menu shortcut for a product-specific shell—say, SharePoint

Server—and you don’t know where that product installed its PowerShell module,

open the properties for the Start menu shortcut. As we showed you earlier in this

chapter, the Target property of the shortcut will contain the Import-Module command used to load the module, and that will show you the module name and path.

Modules can also add PSDrive providers. You’d use the same technique you used

for PSSnapins to identify any new providers: run Get-PSProvider.



7.5



Command conflicts and removing extensions

Take a close look at the commands we added for both SQL Server and Active Directory. Notice anything special about the commands’ names?

Most PowerShell extensions—Exchange Server being a notable exception—add a

short prefix to the noun portion of their command names. Get-AD User, for example,

or Invoke-Sql Cmd. These prefixes may seem awkward, but they’re designed to prevent

command conflicts.

For example, suppose you loaded two modules that each contained a Get-User

cmdlet. With two commands having the same name and being loaded at the same time,

which one would PowerShell execute when you run Get-User? The last one loaded, as

it turns out. But the other commands having the same name aren’t inaccessible. To specifically run either command, you’d have to use a somewhat awkward naming convention that requires both the snap-in name and the command name. If one Get-User

came from a snap-in called MyCoolPowerShellSnapin, you’d have to run this:

MyCoolPowerShellSnapin\Get-User



That’s a lot of typing, and it’s why Microsoft suggests adding a product-specific prefix,

like AD or SQL, to the noun of each command. Adding prefixes helps prevent a conflict and helps make commands easier to identify and use.

If you do wind up with a conflict, you can always choose to remove one of the conflicting extensions. You’d run Remove-PSSnapin or Remove-Module, along with the

snap-in or the module name, to unload an extension.



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Playing with a new module



7.6



81



Playing with a new module

Let’s put your newfound knowledge to use. We’ll assume that you’re using the newest

version of Windows, and we’d like you to follow along with the commands we present

in this section. More importantly, we want you to follow the process and the thinking

that we’ll explain, because this is how we teach ourselves to use new commands without rushing out and buying a new book for every single product and feature that we

run across. In the concluding lab for this chapter, we’ll have you repeat this same process on your own, to learn about an entirely new set of commands.

Our goal is to clear the DNS name resolution cache on our computer. We’ve no

idea if PowerShell can even do this, so we’ll start by asking the help system for a clue:

PS C:\> help *dns*

Name



Category



Module



---dnsn

Resolve-DnsName

Clear-DnsClientCache

Get-DnsClient

Get-DnsClientCache

Get-DnsClientGlobalSetting

Get-DnsClientServerAddress

Register-DnsClient

Set-DnsClient

Set-DnsClientGlobalSetting

Set-DnsClientServerAddress

Add-DnsClientNrptRule

Get-DnsClientNrptPolicy

Get-DnsClientNrptGlobal

Get-DnsClientNrptRule

Remove-DnsClientNrptRule

Set-DnsClientNrptGlobal

Set-DnsClientNrptRule



-------Alias

Cmdlet

Function

Function

Function

Function

Function

Function

Function

Function

Function

Function

Function

Function

Function

Function

Function

Function



-----DnsClient

DnsClient

DnsClient

DnsClient

DnsClient

DnsClient

DnsClient

DnsClient

DnsClient

DnsClient

DnsClient

DnsClient

DnsClient

DnsClient

DnsClient

DnsClient

DnsClient



Ah-ha! As you can see, we have an entire DnsClient module on our computer. The

previous list shows the Clear-DnsClientCache command, but we’re curious about

what other commands are available. In order to find out, we’ll manually load the module and list its commands:

TRY IT NOW Go ahead and follow along as we run these commands. If you

don’t have a DnsClient module on your computer, then you’re using an older

version of Windows. Consider getting a newer version, or even a trial version

that you can run inside a virtual machine, so that you can follow along.

PS C:\> import-module -Name DnsClient

PS C:\> get-command -Module DnsClient

Capability



Name



---------CIM

CIM

CIM



---Add-DnsClientNrptRule

Clear-DnsClientCache

Get-DnsClient



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CHAPTER 7

CIM

CIM

CIM

CIM

CIM

CIM

CIM

CIM

CIM

CIM

CIM

CIM

CIM

Cmdlet



Adding commands



Get-DnsClientCache

Get-DnsClientGlobalSetting

Get-DnsClientNrptGlobal

Get-DnsClientNrptPolicy

Get-DnsClientNrptRule

Get-DnsClientServerAddress

Register-DnsClient

Remove-DnsClientNrptRule

Set-DnsClient

Set-DnsClientGlobalSetting

Set-DnsClientNrptGlobal

Set-DnsClientNrptRule

Set-DnsClientServerAddress

Resolve-DnsName



NOTE We could have asked for help on Clear-DnsClientCache, or even run

the command directly. PowerShell would have loaded the DnsClient module

for us in the background. But, because we’re exploring, this approach lets us

view the module’s complete list of commands.



This list of commands looks more or less the same as the earlier list. Fine; let’s see

what the Clear-DnsClientCache command looks like:

PS C:\> help Clear-DnsClientCache

NAME

Clear-DnsClientCache

SYNTAX

Clear-DnsClientCache [-CimSession ] [-ThrottleLimit

] [-AsJob] [-WhatIf] [-Confirm] []



Seems straightforward, and we don’t see any mandatory parameters. Let’s try running

the command:

PS C:\> Clear-DnsClientCache



OK, no news is usually good news. Still, it’d be nice to see that the command did something. Let’s try this instead:

PS C:\> Clear-DnsClientCache -verbose

VERBOSE: The specified name resolution records cached on this machine will

be removed.

Subsequent name resolutions may return up-to-date information.



The -verbose switch is available for all commands, although not all commands do

anything with it. In this case, we get a message indicating what’s happening, which

tells us the command did run.



7.7



Profile scripts: preloading extensions

when the shell starts

Let’s say you’ve opened PowerShell, and you’ve loaded several favorite snap-ins and

modules. If you took that route, you’d be required to run one command for each



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Profile scripts: preloading extensions when the shell starts



83



snap-in or module you want to load, which can take a few minutes of typing if you have

several of them. When you’re done using the shell, you close its window. The next

time you open a shell window, all of your snap-ins and modules are gone, and you

have to run all those commands again to load them back. Horrible. There must be a

better way.

We’ll show you three better ways. The first involves creating a console file. This only

memorizes PSSnapins that are loaded—it won’t work with any modules you may have

loaded. Start by loading in all of the snap-ins you want, and then run this command:

Export-Console c:\myshell.psc



Running the command creates a small XML file that lists the snap-ins you loaded into

the shell.

Next, you’ll want to create a new PowerShell shortcut somewhere. The target of

that shortcut should be

%windir%\system32\WindowsPowerShell\v1.0\powershell.exe

➥-noexit -psconsolefile c:\myshell.psc



When you use that shortcut to open a new PowerShell window, your console will load,

and the shell will automatically add any snap-ins listed in that console file. Again, modules aren’t included. What do you do if you have a mix of snap-ins and modules, or if

you have some modules that you always want loaded?

Keep in mind that PowerShell will auto-load modules that are in one of

the PSModulePath locations. You only need to worry about the following

steps if you want to preload modules that aren’t in one of the PSModulePath

locations.

TIP



The answer is to use a profile script. We’ve mentioned those before, and we’ll cover

them in more detail in chapter 25, but for now follow these steps to learn how to use

them:

1



2



3



4



In your Documents folder, create a new folder called WindowsPowerShell (no

spaces in the folder name).

In the newly created folder, use Notepad to create a file named profile.ps1.

When you save the file in Notepad, be sure to enclose the filename in quotation

marks (“profile.ps1”). Using quotes prevents Notepad from adding a .txt filename extension. If that .txt extension gets added, this trick won’t work.

In that newly created text file, type your Add-PSSnapin and Import-Module

commands, listing one command per line in order to load your preferred snapins and modules.

Back in PowerShell, you’ll need to enable script execution, which is disabled by

default. There are some security consequences to this that we’ll discuss in chapter 17 but for now we’ll assume you’re doing this in a standalone virtual

machine, or on a standalone test computer, and that security is less of an issue.

In the shell, run Set-ExecutionPolicy RemoteSigned. Note that the command



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