One question that comes up fairly often when dealing with (or writing!) secure cmdlets is how to properly handle usernames and passwords. The solution there is to use (or make) the -Credential parameter of type PSCredential. A PSCredential object helps ensure that your password stays protected in memory, unlike cmdlets that accept a straight username / password combination.

If a parameter is of type PSCredential, PowerShell supports several types of input:

• empty: If you supply no input to a mandatory -Credential parameter, PowerShell prompts you for the username and password.
• string: If you supply a string to the -Credential parameter, PowerShell treats it as a username and prompts you for the password.
• credential: If you supply a credential object to the -Credential parameter, PowerShell accepts it as-is.

This is great for interactive use, but what if you want to write an automated script for a cmdlet that accepts a -Credential parameter? The solution lies in passing a pre-constructed PSCredential object. The solution to this is covered by recipe 16.9 in the PowerShell Cookbook:

Securely Store Credentials on Disk

Problem

Your script performs an operation that requires credentials, but you don’t want it to require user interaction when it runs.

Solution

To securely store the credential’s password to disk so that your script can load it automatically, use the ConvertFrom-SecureString and ConvertTo-SecureString cmdlets.

Save the credential’s password to disk

The first step for storing a password on disk is usually a manual one. Given a credential that you’ve stored in the $credential variable, you can safely export its password to password.txt using the following command:

Recreate the credential from the password stored on disk

In the script that you want to run automatically, add the following commands:

These commands create a new credential object (for the CachedUser user) and store that object in the $credential variable.

Discussion

When reading the solution, you might at first be wary of storing a password on disk. While it is natural (and prudent) to be cautious of littering your hard drive with sensitive information, the ConvertFrom-SecureString cmdlet encrypts this data using Windows’ standard Data Protection API. This ensures that only your user account can properly decrypt its contents.

While keeping a password secure is an important security feature, you may sometimes want to store a password (or other sensitive information) on disk so that other accounts have access to it anyway. This is often the case with scripts run by service accounts or scripts designed to be transferred between computers. The ConvertFrom-SecureString and ConvertTo-SecureString cmdlets support this by allowing you to specify an encryption key.

Although the solution stores the password in a specific named file, it is more common to store the file in a more generic location—such as the directory that contains the script, or the directory that contains your profile.

To load password.txt from the same location as your profile, use the following command:

To learn how to load it from the same location as your script, see “Find your Script’s Location.”

For more information about the ConvertTo-SecureString and ConvertFrom-SecureString cmdlets, type Get-Help ConvertTo-SecureString or Get-Help ConvertFrom-SecureString.

After what seems like an eternity, I finally got to start my official flight training. As a Canadian (AKA "Alien,") applying for flight school also means getting your fingerprints taken and being put in a special registration system. My training permission cleared late last week, so I booked my first lessons as soon as I could. In fact, for a government agency, the flight registration process was surprisingly efficient. Finding a place to get TSA-approved fingerprints outside of work hours? Well, that's a different story.

Anyways.

One of the things I really missed about my intro flights was a good understanding of exactly where I traveled during the flight. I remembered some landmarks, but didn't really catch on to many streets or things I knew from my ground travels. Recording my tracks through a GPS system seemed to be the best approach, so I finally settled on a Lowrance Airmap 2000C. Its features rival most of the top-end aircraft GPS products (aside from XM weather and traffic, which I'm not in the market for,) at a fraction of the price. For about the same cost, I would have been able to use some computer-based GPS software on my Tablet PC, but messing around with a Tablet PC in the cockpit seems to be a lot more trouble than it's worth.

I took it on a long camping trip during the Memorial Day long weekend, and it was fun watching it trace my path around the Puget Sound. It warned me plenty as I passed through the restricted airspaces (McChord airforce base, SeaTac airport, etc,) so luckily I wasn't actually flying.

On Thursday, I went for my first real lesson, flying AcuWings' Piper Warrior PA28-151. This is the kind of plane I want to do most of my training on -- as the Cirrus SR20 (while newer and nicer) felt like it might prevent me from learning some of the subtle basics -- like rudder control, or use of the nose-wheel while on the ground.

In the introductory flights, the instructor does almost all of the ground work, aside from giving you a brief overview of what they are doing. For your first training flight, though, you start to take over the technical preparations: aircraft examination, engine start procedures, pre-takeoff work, and the post-flight run-down. We spent about 45 minutes on these preparations, learning the how and why behind 80+ items in the pre-flight and post-flight checklists.

In the air, we practiced straight and level flight, ascents, descents, and (level, ascending, descending) turns. Like the flight-preparation work, non-introductory training means that you begin to take over much more of the landing preparations. During this flight, we did 2 landings, one being a touch-and-go. For both, I flew the traffic pattern, lined up the approach, and helped guide us toward the runway. I did a little less of the actual landing than I had done during my introductory flights, but I think that was probably because of higher wind. This flight gave me 0.8 hours of qualified dual-instruction to apply to my flight training.

On Sunday, we put in another 1.1 hours of dual instruction, with the learning curve continuing just as steep. Since I had been taught the checklists, pre-flight this time was all my own – including the inevitable splashing of leaded, high-octane Avgas on my hands while testing for fuel contaminants. As we prepared for takeoff, I was shown how to talk with the tower, request permission to taxi, take-off, and practice landings. That's a massive system of verbal cryptography that will take a while to get used to, but you feel like part of a club when you're doing it.

While in the air, we practiced slow flight (near-stall conditions,) stalls, and recovering from stalls. These are the most common "emergency" situations in flight, and are relatively easy to recover from as long as you know what you are doing. If you haven't practiced them, then you'll just panic and donate some iron to the earth's mantle.

After practicing those, we started working on landings. As a skill in flying, landings are a unique breed. They are a skill within a skill: a technique that gets lavish attention in the context of flying, but completely independent of it. Pilots obsess about landings the same way that cigar aficionados gush about about the tower of ash emanating from their cigar, or how developers delight in "Perl Golf,"

It's a journey that's just beginning -- I can't wait for more.

Once in awhile, you'll see a PowerShell screenshot that is still black and boring like the traditional cmd.exe prompt. Other times, you'll see the fancy blue window you've come to love. Why the difference? And if you're suffering from black window syndrome, what can you do about it?

Before shipping Version 1, our marketing and design teams set to make the PowerShell window a unique and marquee experience. What form did this take?

• Blue. Specifically, Red: 1, Green: 36, Blue: 86. -- In hex, 012 456. That number is much too cool to be a coincidence, but I haven't done the social archeology to find out why :)
• Lucida Console. Lucida Console is infinitely more readable than the raster fonts, and ships with all versions of Windows. Consolas is a beautiful alternative, but isn't broadly available.
• Window Size. Long gone are the days of 640x480 monitors being the most common, so PowerShell's default window gives about 800x600 of usable space.
• Screen Buffer. Likewise, long gone are the days of 256mb of memory being the most common, so PowerShell's default window gives a dreamy 60 pages of history buffer. This is a shell you want to live in. And when you live in a shell, you  want to be able to see what you've done.
• Quick Edit. Quick Edit mode lets you copy and paste easily to and from the console window. It is the setting that most console users enable once they realize it exists, and long gone are the days of mouse-driven console applications.

Now, even with all of these improvements, you still see screen shots of PowerShell prompts blinking desolate in the confines of a traditional black console window. Why is this?

PowerShell customizes its window through the shortcut properties in its Start Menu link. When you launch PowerShell through the Start | Run dialog or some other app launcher, these shortcut properties don't apply. Surprisingly, Windows does not support a mechanism to make these console customizations machine-wide. Windows supports per-user console customizations in the the HKCU hive of the registry, but there's usually no "Current User" during a PowerShell install. And even if there were, any customizations would not apply to user accounts created after PowerShell was installed.

So how do you get PowerShell's Noble Blue if you prefer Start | Run? Here's a script from the PowerShell Cookbook that does exactly that -- for your current user account.:

## From Windows PowerShell, The Definitive Guide (O'Reilly)
## by Lee Holmes (http://www.leeholmes.com/guide)

Push-Location
Set-Location HKCU:\Console
New-Item ".\%SystemRoot%_system32_WindowsPowerShell_v1.0_powershell.exe"
Set-Location ".\%SystemRoot%_system32_WindowsPowerShell_v1.0_powershell.exe"

New-ItemProperty . ColorTable00 -type DWORD -value 0x00562401
New-ItemProperty . ColorTable07 -type DWORD -value 0x00f0edee
New-ItemProperty . FaceName -type STRING -value "Lucida Console"
New-ItemProperty . FontFamily -type DWORD -value 0x00000036
New-ItemProperty . FontSize -type DWORD -value 0x000c0000
New-ItemProperty . FontWeight -type DWORD -value 0x00000190
New-ItemProperty . HistoryNoDup -type DWORD -value 0x00000000
New-ItemProperty . QuickEdit -type DWORD -value 0x00000001
New-ItemProperty . ScreenBufferSize -type DWORD -value 0x0bb80078
New-ItemProperty . WindowSize -type DWORD -value 0x00320078
Pop-Location

If you're testing your PowerShell scripts (manually or automatically,) one of the first questions you'll end up asking yourself is, "did I test enough?"

This is common problem in all of software development. To the rescue is a simple metric known as "Code Coverage" – a measure of how much code you exercised during the testing of that code.

However, the measurement is just the end result – you need a tool to get you there. When it comes to measuring code coverage in PowerShell scripts, though, there simply aren't any tools yet.

Like performance measurement tools, Code Coverage tools are sometimes driven by instrumentation of the source code, and sometimes driven by sampling the code during runtime. Instrumentation gives the highest accuracy, but we can go a long way by runtime analysis alone. To accomplish that, we'll use our favourite feature to abuse – PowerShell script tracing. The last time we pushed it, we got a sampling profiler out of the deal. Let's do it again for code coverage.

Take, for example, the following source code:

trap { "Error handling!"; continue }                                  
                                                                      
"Got here"                                                            
                                                                      
if($args[0] -eq "Test")                                               
{                                                                     
   "Got TEST as an argument"                                          
}                                                                     
elseif($args[0] -eq "Err0r")                                          
{                                                                     
   throw "Catch Me!"                                                  
}                                                                     
else                                                                  
{                                                                     
   "Didn't get TEST as an argument"                                   
}     

We want to run through three parameters that it takes, and make sure we're exercising everything. Notice how we're even being diligent by testing the "Error" case!

PS C:\temp> $tests = @()                                              
PS C:\temp> $tests += { .\Test-CodeCoverage.ps1 Test }                
PS C:\temp> $tests += { .\Test-CodeCoverage.ps1 SomethingElse }       
PS C:\temp> $tests += { .\Test-CodeCoverage.ps1 Error }               
PS C:\temp>                                                           
PS C:\temp> .\Get-ScriptCoverage.ps1 .\Test-CodeCoverage.ps1 $tests 

What does that give us?

trap { "Error handling!"; continue }                                  
                                                                      
"Got here"                                                            
                                                                      
if($args[0] -eq "Test")                                               
{                                                                     
   "Got TEST as an argument"                                          
}                                                                     
elseif($args[0] -eq "Err0r")                                          
{                                                                     
   throw "Catch Me!"                                                  
}                                                                     
else                                                                  
{                                                                     
   "Didn't get TEST as an argument"                                   
}                                                                     
Coverage Statistics: 66.6666666666667%                                
PS C:\temp>   

Ouch! Why is the error handling code (in red) not being hit? Ah, after further investigation, it turns out that we have a typo in our string comparison. We fix it:

...
elseif($args[0] -eq "Err0r")
...

Becomes

...
elseif($args[0] -eq "Error")
...

And run code coverage again:

trap { "Error handling!"; continue }                                  
                                                                      
"Got here"                                                            
                                                                      
if($args[0] -eq "Test")                                               
{                                                                     
   "Got TEST as an argument"                                          
}                                                                     
elseif($args[0] -eq "Error")                                          
{                                                                     
   throw "Catch Me!"                                                  
}                                                                     
else                                                                  
{                                                                     
   "Didn't get TEST as an argument"                                   
}                                                                     
Coverage Statistics: 100%                                             
PS C:\temp>    

Much better.

Here is the script – under 80 lines of (heavily commented) code:

## Get-ScriptCoverage.ps1                                             
## Test the script named by $testScript for code coverage.            
## The command given by $command must exercise this named             
## script.                                                            
param([string] $testScript, [ScriptBlock[]] $command)                 
                                                                      
# Store the content of the script to be tested                        
$fileContent = gc $testScript -ea Stop                                
                                                                      
## Start a transcript, and log it to a file                           
$tempFile = [IO.Path]::GetTempFilename()                              
Start-Transcript $tempFile                                            
                                                                      
## Turn on line-level tracing, run the command(s),                    
## then turn off line-level tracing again.                            
Set-PsDebug -Trace 1                                                  
$command | Foreach-Object { & $_ }                                    
Set-PsDebug -Trace 0                                                  
                                                                      
## Stop the transcript                                                
Stop-Transcript                                                       
                                                                      
## Get the result of the script coverage run                          
$coverageContent = (gc $tempFile) -match "^DEBUG:"                    
Remove-Item -LiteralPath $tempFile                                    
                                                                      
Clear-Host                                                            
                                                                      
## Clean up interference from other scripts                           
$scriptLines = @()                                                    
$processedLines = @{}                                                 
                                                                      
foreach($originalLine in $coverageContent)                            
{                                                                     
    # Make sure we only process unique lines in the                   
    # transcript                                                      
    if($processedLines[$originalLine]) { continue }                   
    $processedLines[$originalLine] = $true                            
                                                                      
    ## Recover as much as possible from the original script line      
    ## without its debugging information                              
    $originalLine = $originalLine -replace " <<<< ",""                
    $line = $originalLine -replace '\D*\d+\+ (.*)','$1'               
                                                                      
    ## Go through each line in the original script, and see if        
    ## this is actually in the script                                 
    foreach($fileLine in $fileContent)                                
    {                                                                 
        ## If it is, add the debug line to the list of lines          
        ## covered by this scenario                                   
        if($fileLine.Contains($line))                                 
        {                                                             
            $scriptLines += $originalLine                             
        }                                                             
    }                                                                 
}                                                                     
                                                                      
## Find out which line numbers were covered                           
$coveredLines = $scriptLines |                                        
    % { $_ -replace '\D*(\d+)\+ .*','$1' } | Sort -Unique             
                                                                      
$coverageCount = 0                                                    
$possibleCoveredLines = 0                                             
for($counter = 1; $counter -le $fileContent.Count; $counter++)        
{                                                                     
    $color = "Red"                                                    
    $line = $fileContent[$counter - 1]                                
                                                                      
    ## Ignore comments, blank lines, curly                            
    ## braces, and fall-through conditional statements                
    ## in coverage computation (as they are never                     
    ## traced in Set-PsDebug tracing                                  
    if(($line -notmatch '^\s*#') -and                                 
       ($line -notmatch '^\s*{\s*$') -and                             
       ($line -notmatch '^\s*}\s*$') -and                             
       ($line -notmatch '^\s*else') -and                              
       ($line -notmatch '^\s*param\(') -and                           
       ($line.Trim()))                                                
    {                                                                 
        $possibleCoveredLines++                                       
    }                                                                 
    else { $color = "Gray" }                                          
                                                                      
    ## If this line was hit in code coverage, colour it               
    ## green                                                          
    if($coveredLines -contains $counter)                              
    {                                                                 
        $color = "Green"                                              
        $coverageCount++                                              
    }                                                                 
                                                                      
    ## Display the line in the appropriate colour                     
    Write-Host -Fore $color $line                                     
}                                                                     
                                                                      
## Output the coverage statistics                                     
Write-Host ("Coverage Statistics: " +                                 
    "$($coverageCount / $possibleCoveredLines * 100)%")               

For a long time, I've been thinking about learning to fly. One of the random long-distance-drive conversations I like to have is, "What job would you do if you were for some reason prevented from doing what you do now?" For me, flying has always been something I would entertain, but only romantically. The downsides to doing it professionally are huge -- the time away from your family and strict seniority-based promotions being the two largest factors. So instead, I wanted to reward myself with flying lessons the next time I thought it was appropriate. A King of the Hill episode, of all things, changed my mind on that.

In that episode, Hank (the father) and Peggy (the mother) were going through marital problems, and spoke with a counselor. The counselor asked them what they wanted to do when they retired -- something they had been planning toward for a long time. Their dream was to buy some motorcycles and tour the United States together. The counselor's suggestion was simple -- holding off on buying the bikes doesn't really help anything, so just buy the darn things and start enjoying yourselves! The cross-country tours can wait until you have the time to do them, but little local trips can happen right now.

That started the slow chemical reaction in my brain, which ultimately led me to start investigating flying lessons more seriously.

My typical obsessive online research turned up lots of information about learning to fly. Tom Unger’s “Flying Lessons” journal was indispensable, gave a lot of great background information, and what to expect with the process. However, I found very little about picking a flight school around the Seattle area, and sent a mail to an internal mailing list asking for opinions. Four suggestions came up most frequently:

• Pro-Flight Aviation: http://www.flyproflight.com/
• Galvin Flying Service: http://www.galvinflying.com/
• Acu-Wings: http://www.acuwings.com/
• Alternate Air: http://www.alternateair.com/

I ruled out Galvin immediately – their responses to customer complaints on http://www.airnav.com/airport/KBFI/GALVIN were ridiculous and showed complete disregard for their customers.

I ended up looking for operations out of the Renton Municipal Airport (KRNT) as my primary factor. It’s close to my house, and commute time seems to be the most important element in choosing a base. Airport traffic and other factors can be learned at other airports (such as Crest Airpark for its crazy small field, and Boeing Field for its busy airspace,) since most of your practice take-offs and landings come from explicit training exercises (as opposed to being dictated by the base you fly from.)

I first checked out Pro-Flight during a 9:00 AM intro flight, taking up a well-loved Cessna 172. Introductory flights are an amazing deal – even as a leisure activity. They cost under $100 for a scenic tour of the Puget Sound, and you get to do most of the flying yourself.

The biggest challenge (as compared to driving a car) was adapting to a new mental model, and adapting to a very manual control system. When taxiing, having 4 control surfaces at my feet was pretty complex – seeing as I kept on thinking of it like controlling handles on a bike steering column. I would instinctively push right expecting to turn left, but got the hang of it more when I thought about it as differential braking (even when I was using the nose wheel part of the control.) My only point of minor helmet fire came at this point – when we needed to use differential braking to make a turn, but my feet were only on the nose wheel portion of the control (as suggested by the instructor.)

Oh, and ignoring my internal alarm bells is hard enough when starting an automatic transmission car without depressing a clutch – an airplane was much worse.

What surprised me most was how much input you had to give the controls. It felt like there was a good 8 inches of travel in the foot pedals – much more than I was expecting. I was sure I was going to rip the knob off of the dash when I was priming the engine.

After we taxied, takeoff went pretty well. There was no traffic, so we didn’t burn engine hours waiting in line. Actually leaving the pavement was weird, as I again was expecting to need a subtle touch. After pushing the throttle forward slowly like you see them do on big airplanes, the instructor told me to just gun it :) The climb felt surprisingly manual as well, although the instructor did give me a rate of ascent to aim for, which helped a lot. Once I visually leveled off, the instructor pointed out that I was still climbing.  The nose definitely points a lot lower during steady flight than it does during takeoff, but adapting to that came shortly.

We did some minor orientation and directional work, and even got to do some nice steep turns. The ceiling was really indefinite, and we had to avoid some cloud cover. The runway approach went really well as we approached from the North. I guess since there was no traffic, we basically did the 45 degree entry directly into an extended final for the traffic pattern. Lining up felt pretty natural, although I made the approach too low – I was aiming for the numbers instead of the first dash.

So all-in-all, it was a great time up – and they seem like a very capable flight school.

The next day, I took a flight with AcuWings, and I can understand why there is so much support for them. Their office was a little hard to find at first (barely any signs on an already nondescript office building,) but they seemed well-run. Their office was off-base, so we had a very short drive across the road to the actual airplanes. They will be getting a building on the field in the near future, so that will be convenient. I followed the owner to the field who, despite his precision flying and deep knowledge of flight rules, failed to use his signal light even once.

For that intro flight, we flew their Cirrus SR20 (since I wanted to try a completely different airplane.) Different it was – an ’07 model, tons of electronics, tons of power, and no traditional yoke! You control the throttle with your right hand, and control the direction with a joystick-like device on your left. The weather was beautiful: in the mid-60s with unlimited ceiling, and 10 miles of visibility. This made for a much busier airport, which was also good to experience.

My daughter joined us on this ride -- an experience I was thrilled to have been able to share with her.

The aircraft was a lot more responsive than the Cessna, so I initially pitched it up to like 1100 ft/min correcting to the proper 700 ft/min or so during takeoff. We climbed to 3500 feet, and were treated to an awesome view of Mount Rainier. With all of the interactive electronics and gadgets, I had to consciously stop myself from getting too absorbed in the pretty displays, and instead use the cockpit window for what it was intended for :) We did some more level turns, played with the autopilot a bit, and practiced throttle control.

I was amazed to learn that airplanes will “skip” in the atmosphere. If you let them go with wings level and drop the power, they will just settle on a new lower altitude that matches the new power.

After about half an hour in the air, we came back to the Renton base and ran a more typical approach. We flew parallel to the runway (which I was surprised to realize was 30ish degrees off of the North-South axis,) and made a short final from the South due to heavy traffic. The landing went well, probably because it was almost entirely under the control of my instructor :)

After landing, it became very clear to me that this hobby has much more in store for me.

A few years ago, we experimented with a "Live" version of Get-ChildItem that retrieved elegant textual context-based advertisements from the internet as you used PowerShell.

This has been very successful, but unfortunately, a small subset of our trial user population has experienced crashing behaviour due to these new shell modifications. We have been unable to reproduce the issue in our labs, so the users in question have sent us screen casts of the crash. Even still, we've been looking at the code so long that we still can't confirm the problem.

It would really help the PowerShell team if you could take a look and help us identify the issue.

I've posted the screen cast here: http://www.leeholmes.com/projects/powershell_crash/. Make sure you have sound enabled, as that is supposedly an important factor.

[Download: http://www.leeholmes.com/projects/SyntaxHighlight/Start-Colourizer.zip]

In our most recent CTP, we exposed PowerShell's parsing and tokenizing API for the great benefit of ISVs and hobbyists alike. As an initial demonstration of it, Show-ColorizedContent let you display nicely formatted code listing in your console:

PS C:\Temp> .\Show-ColorizedContent.ps1 Show-ColorizedContent.ps1 `
>> -HighlightRanges (4..5+1+30..33)
>>

001 > #requires -version 2.0
002 |
003 | param(
004 >     $filename = $(throw "Please specify a filename."),
005 >     $highlightRanges = @(),
006 |     [System.Management.Automation.SwitchParameter] $excludeLineNumbers)
007 |
008 | # [Enum]::GetValues($host.UI.RawUI.ForegroundColor.GetType()) | % { Write-Host -Fore $_ "$_" }
(...)
026 | $highlightColor = "Green"
027 | $highlightCharacter = ">"
028 |
029 | ## Read the text of the file, and parse it
030 > $file = (Resolve-Path $filename).Path
031 > $content = [IO.File]::ReadAllText($file)
032 > $parsed = [System.Management.Automation.PsParser]::Tokenize($content, [ref] $null) |
033 >     Sort StartLine,StartColumn
034 |
035 | function WriteFormattedLine($formatString, [int] $line)
036 | {
037 |     if($excludeLineNumbers) { return }
038 |
039 |     $hColor = "Gray"
040 |     $separator = "|"

While this is very cool, we can actually push the parsing and tokenizing API even further. How about real time?

The first time I got this working, I actually giggled a little with glee. We're all so used to instant gratification when it comes to syntax highlighting that we sometimes forget about it. Until you drop into an environment that doesn't support it -- such as Notepad.exe or the PowerShell console. But with enough chewing gum and rubber bands, we can at least bring it into the PowerShell console.

As an aside, the V2 CTP also includes an early alpha version of PowerShell's new graphical host, Graphical PowerShell. Graphical PowerShell handles syntax highlighting swimmingly, and then some. If you want even more usability improvements (such as window resizing, tabs, and direct Unicode support,) that's where it'll be.

The primary problem with creating a real time colourizer is that PowerShell doesn't generate any events or notifications when you press a key. This makes cooperative multithreading difficult, so instead we need to take a parasitic approach and dig around in the console's screen buffer.

PowerShell doesn't support script threading either, though, so the step toward real-time syntax highlighting in your console is a slightly modified version of Jim Truher's "Background Jobs and PowerShell" script.

For each job that you create, Jim's script creates a new System.Management.Automation.Runspaces.Runspace instance, and then executes the job in the pipeline. Since the runspace class offers an asynchronous (non-blocking) invoke method, this effectively lets us run PowerShell code in the background of our current process. As written, though, Jim's background job support doesn't offer access to the variables and information of the runspace that launched the job. While normally useful, it does limit the usefulness of jobs for parasitic groveling! So, our main change in the New-Job script is to add a variable to the context of new jobs: $executionContextProxy. Through this variable, child jobs can access the variables and other information of the parent that spawned them. This update is included in the attached zip file.

Once we can launch jobs in the background that have access to our environment, the next step is the actual colourizer. This script runs as the background job. It starts at the bottom of the console buffer (where your cursor is,) and scans upward (and left) until it finds the last line of your prompt. It takes that rectangle, uses the parser API to determine how to colourize it, and then swiftly replaces that section of your console screen buffer with the colourized version.

I say "quickly" here to mean "as quickly as possible." There is a slight chance that the background job will swap in the colourized buffer after you've typed some more. It takes some pretty drastic measures to avoid this, but the occasional visual glitch will happen. This is only visual, however. Once you press ENTER, PowerShell will still execute the command you typed.

Many prompts use the Write-Host to add colourized prompts to the console, and return only a single space in the prompt() function. Since the colourizer can't know exactly how your prompt will appear on the screen, you need to tell it what the last line looks like. In your prompt function, set a global variable (called "promptMarker") to have the same text as the last line of your prompt. For example, if your prompt displays:

PS:15 >

on the screen, then set $GLOBAL:promptMarker = "PS:15 >"

Now, with New-Job.ps1 and Start-Colourizer.ps1 in your path (and a prompt that updates the promptMarker variable,) start the colourizer as a job:

Now, PowerShell updates your console with context-sensitive syntax highlighting as you type.

If you find the default console colours to be ugly, the included Set-ConsoleColourTable.ps1 script tones them down to something much easier on the eyes.

[Download: http://www.leeholmes.com/projects/SyntaxHighlight/Start-Colourizer.zip]

Enjoy!

When O’Reilly put up the overview page for the Windows PowerShell Cookbook, the sample chapter was originally “Looping and Flow Control.” While a useful chapter in its own right, it didn’t really highlight the solution-oriented focus the book takes.

They’ve now updated the sample chapter to one much more representative: Environmental Awareness.

The goal of this chapter is to help you work with the global environment (environment variables and common system paths,) and script’s environment (its location, name, and invocation info.)

It covers:

14. Environmental Awareness
       14.0 Introduction  
       14.1 View and Modify Environment Variables  
       14.2 Access Information About Your Command's Invocation  
       14.3 Program: Investigate the InvocationInfo Variable  
       14.4 Find Your Script's Name  
       14.5 Find Your Script's Location  
       14.6 Find the Location of Common System Paths  
       14.7 Program: Search the Windows Start Menu  
       14.8 Get the Current Location  
       14.9 Safely Build File Paths Out of Their Components  
       14.10 Interact with PowerShell's Global Environment 

You can download it by following the sample chapter link at the book’s overview page.

A question recently came up asking why the -eq operator doesn't work for two different (but equal) SecureStrings.

By default, almost all environments (the .NET Framework included) test if two things are exactly the same – that they are stored in the same place in memory. This is called reference equality.

[D:\documents\WindowsPowerShell]

PS:14 > $test = Read-Host -AsSecureString

****

[D:\documents\WindowsPowerShell]

PS:15 > [Object]::ReferenceEquals($test, $test)

True

[D:\documents\WindowsPowerShell]

PS:16 > $test -eq $test

True

That’s not usually what people want, so each individual type of object is (optionally) responsible for supporting a value-based equality test. They do this by implementing interfaces (software contracts) called IComparable and / or IEquatable:

[D:\documents\WindowsPowerShell]

PS:17 > $string1 = "Test"

[D:\documents\WindowsPowerShell]

PS:18 > $string2 = "Test"

[D:\documents\WindowsPowerShell]

PS:19 > [Object]::ReferenceEquals($string1, $string2)

False

[D:\documents\WindowsPowerShell]