If someone else had a cmdlet called, say, out-banner, and that cmdlet was already loaded in a snap-in (perhaps mandated by site policy), would I be able to register and add the Grrr snapin, which also defines it?

I’ve scanned the available documentation and the language grammar, used introspection in the shell and so on, but could not find anything to deal with this problem.

With projects like PowerShell Community Extensions seemingly laying claim to hundreds of common nouns and verbs, I was concerned that the scope for writing unique cmdlets would dry up real fast.

To determine what would happen, I registered and added Soapyfrog.Grrr, then wrote a new snapin, Soapyfrog.Conflict, with a single cmdlet, out-banner, conflicting with the one in Grrr.

I registered and added this, and was surprised that no warning of a conflict was given. To see if both were added, I tried this:

PS> get-command out-banner

CommandType     Name                        Definition
-----------     ----                        ----------
Cmdlet          Out-Banner                  Out-Banner [-Text] <Str...
Cmdlet          Out-Banner                  Out-Banner [-Text] <Str...

Interesting. Both are available, so what happens when I try to invoke it?

PS> out-banner hello
The term 'out-banner' resolved to a cmdlet name that is ambiguous. Pos
sible matches include: Soapyfrog.Grrr\Out-Banner soapyfrog.conflict\Ou
t-Banner.
At line:1 char:11
+ out-banner  <<<< hello

OK, so at this point, we know it’s possible to break existing PowerShell scripts by simply registering and adding a new snapin with a same-named cmdlet. Not good. Is there a work-around?

PS> Soapyfrog.Grrr\out-banner hello -fg 'o'
o   o ooooo o     o      ooo
o   o o     o     o     o   o
ooooo ooo   o     o     o   o
o   o o     o     o     o   o
o   o ooooo ooooo ooooo  ooo

Yes! We can fully qualify the cmdlet name with the snapin name and a backslash.

So, it’s not as bad as I first feared, but as I noted above, you need to be very careful about how you code and run scripts in environments where you can’t predict what snapins are registered and installed.

I suppose you can create the correct shell environment with Export-Console and run your script with:

powershell -psconsolefile xxx.psc1 -noprofile -command myscript.ps1

Or if your script requires a snapin, add the snapin in the script and fully qualify each cmdlet you use.

Grrr 1.1 is now Cmdlet based and comes as a Snap-In. The most obvious benefit from this is performance, as I can now present a playable version of PowerShell Big Invaders.

BigInvaders is one of the demo PowerShell scripts that makes use of the Grrr.

Download this prerelease version 1.1 of the Grrr snap-in.

Update: this should now install on Vista – thanks to Chris Warwick for pointing out some issues

There’s no installer (yet) so to get going, follow this instructions:

Unzip the archive where you want to use it and CD to the top level director where the README file is.

Type: ./installgrrr.ps1 -r

The -r switch forces it to re-register the snap-in if a (possibly) older version exists. It then adds the snap-in to the current shell.

From here you can CD into the demos directory and run any of the scripts. Each one shows a feature of Grrr, but perhaps the most interesting is in the biginvaders directory.

To run BigInvaders, you need to have a very large console. To achieve this you probably need to set the font size of your console window to 6×8.

If you want sound, you need to install DirectX DirectSound. More on why later.

It should work without, silently, but this hasn’t had much testing as all my XP boxes have it installed If there are exceptions, start it with the -nosound switch.

Assuming all is well, type ./biginvaders.ps1 and you should see this title screen:

Hit ESC to quit or Space to play. In play, Space fires a missile and arrow keys move left and right. Hit F to toggle FPS display in the top-righthand corner.

The target FPS is 33. I achieve this easily on my MacPro, and my wife’s Dell (a core 1 duo, 1.66ghz) also just manages.

There are still a few snags to iron out here and I want to add proper PowerShell help and an installer, but it is functional.

I’ve learned a lot about C#, PowerShell SDK and .NET these last weeks and will write about my findings over the next days. It’s not all been rosy.

I’ll also be writing about the features of Grrr, and where I want to go with it.

That’s it for now.