Powershell Escape characters.

A while back I couldn't find a definitive list of the regular escape characters for PowerShell. So I wrote a program that would generate them all and give me a clue for each letter what I might get.

I have since lost the code, and the output was a little cryptic, particularly with nonprinting characters like Tab, space, Carriage return, Line feed, and Bell.

The Bell character "`a" was interesting. But it doesn't always make it back to me from a session.

The first 2 are for the quoting characters, if you need to embed a quote in the string you are creating, this is one easy way to get them placed literally, and not interpreted by the compiler.

As it was noted it the PluralSight Gotcha video, these are limited to Powershell, you will find if you pass a string to .net or some other software, it may have a different escape character, and different behavior.


Notes:

• Single quote ' means that what is enclosed is Literal not to be processed
• Double quote " means that what is enclosed is interpreted.
• The Backtick is ` and not the single quote '  (apostrophe)
• The key is typically on the left side of the keyboard upper left corner. 

PowerShell Escape character table:

ASCII	Letter	Esc	Name	Result ASCII
34	"	`"	Double Quote	34
39	'	`'	Single Quote	39
48	0	`0	Null	00
96	`	``	Back-tick	96
97	a	`a	Bell	07
98	b	`b	Backspace	08
102	f	`f	Line Feed	12
110	n	`n	New Line	10
114	r	`r	Carriage Return	13
116	t	`t	Tab	09
118	V	`v	Vertical tab	11

*   They are Case Sensitive...  "`n" -ne  "`N"  etc. 

Out-Internet_explorer

Output to a web browser? But why?
I was fishing around in the PowerShell Studio Snippets and a ran across one Snippet:called Trace.

I wanted to use this snippet to upgrade the output of my troubleshooting tool, ServerPulse. An update of a script that I originally wrote to give text output. With this connection to Internet Explorer, I could create something that was a bit easier on the eyes and stop the junior engineers from puckering when they looked at it. ServerPulse was a text-based self-updating dashboard which I thought was rather functional. however, I could see a bit of aesthetics to making it browser output.  I think there is a lot of possibilities with formatting the output as HTML and then it could be delivered by file, email,  or to a web browser.

This update would give me time to rethink what and how I was gathering the data. Keeping the live data refreshing feature of the troubleshooting tool would be important.

I did some tweaking on the base snippet.

I played with this on my workstation, and when I tried it on a server I got some weird errors.

Problem is this requires a certain DLL to function - "Microsoft.mshtml.dll"
It may not be loaded on a server or workstation in some conditions. I have read that MS office installs it.  Here is a more detailed article in how to add it if you get the error "Property 'innerhtml' cannot be found on this object; make sure it exists and is settable."
Check out - http://www.dlldownloader.com/microsoft-mshtml-dll/ with a detailed explanation of the problem.

After fixing that, I was able to use it any computer that had the dll, I read that the Microsoft Office suite added this dll, which was the cause of the initial confusion with the server version, Which had no reason for it to have MS office installed.

So I created the following function from the snippet to post things to the Web page. You can repeatedly call this function to update information if you want to refresh or expand on the output. The flexibility of the Web browser interface is almost without limit.

But... You have to feed it HTML.
Besides hello world, I thought a basic clock would be in order.
Clock code to HTML A little adjustment to the function like so:
And when feed the output the clock code to the function it pops up a window like this:
" Out-IE ($report) "

IE WINDOW:

Hard to look at and kind of cryptic. But re-using some old MS script example, I can append a block of formatting to make it a little prettier.

* NOTE: If your playing with this on the Shell prompt, Make sure you get the $IE = ""In there someplace between sessions or you won't get a new window...  which was confusing at first for me.
And this is a feature for being able to update the data.

The Refined  IE output portion now looks like:




Now some more example of use.

Building on that code I added another table and gleaned some additional info from the local system. Then you can loop the code to keep it updating the output on IE. The next step was to add some more useful info: And I added some more useful info. An example finished script:

Output of this looks like:


And this version updates the info on the screen, you can see the values change, and the clock ticking.

Formatting Output in KB, MB, GB, TB ....

One of the things that bugged me about PowerShell since I first worked with it was its penchant to give me File directory listings with the file length in bytes. DIR in the CMD shell did it for me.

The textbook answer, of course, is to simply divide the output by 1KB, 1MB, 1GB  as these constants are set in the environment. The obvious problem with this is that it makes the assumption you know what size you're going to get. or that you want the answer in all the same units. But what if you have limited space to display the info, and you don't want to put  23B in the same column with 1293834556 in the same column.

So recently I set about to find a way to have a function that would auto-scale the Byte prefix. I played with the various number types available and put it to the test to see how high I could go with the prefixes. A list I got from Wikipedia.

Experimenting, I worked out an algorithm for this, and it should work cross-platform.
I will update this when I hear of it being tested in something other than Windows Power Shell (WPS). I created these 2 functions, one to work with KB and the second to work with standard SI 1000 units. The second is just a bonus from figuring out the byte calculations.

I added a few features to the function to make it more flexible in use. I added the "-digits" switch so you could control how many decimal places you got on the output. and I also added the "-Units" switch so that you could change from the default "B" to Bytes or whatever fits your need.

I then wracked my brain with what to call it.
Having watched SAO – Ordinal Scale. On Blu-ray with my wife recently, I looked up Ordinal and it seems to fit. Prefix would also work, but that may have other implications.

While I was tweaking it for this article I thought I could make a minor change and have it do the same autoscale for regular 1000 based items. So this could also be used to deal with anything from Dollars to  Miles or anything you have to describe a large number of.

If you new to functions, you can incorporate this code into your script, or you can load it into memory.  This is called Dot sourcing. Google 'Dot source PowerShell function'

Convert-kBOrdinal.ps1

<#  
    .NOTES
    ===========================================================================
     Created with:  SAPIEN Technologies, Inc., PowerShell Studio 2018 v5.5.150
     Created by:    Rich Stoddart
     Filename:     Convert-kBOrdinal.ps1    
    ===========================================================================
    .DESCRIPTION
        Functions to format output by standard Metric Prefixs for binary (1024) 
        and decimal (1000) units. 
        Created to format data concisely on reports, 
        this will process things to as large a number you cn old in a [decimal] 
        type. 
    .EXAMPLE
        gci |% { New-Object -TypeName PSObject -Property ( @{Length = ($_.Length | Convert-kBOrdinal) ; Name = $_.Name}})
        (gi .\install.exe ).length | Convert-kBOrdinal
#>

function Convert-kBOrdinal
{
    param (
        [Parameter(ValueFromPipeline, Position = 0, Mandatory = $true)]
        [decimal]$Num,
        [Parameter(Position = 1, Mandatory = $false)]
        [int]$digits = 2,
        [Parameter(Position = 2, Mandatory = $false)]
        [string]$Units = "B"
    )
    
    if ($NUM -lt 1E+28)
    {
        [int]$Ordinal = ([math]::Floor((($Num.ToString()).Length - 1)/ 3))
        [string]$Digit = [math]::Round($Num / [math]::pow(1024, $Ordinal), $digits)
        [string]$Suffix = "$(((' KMGTPEZYB').Substring($Ordinal, 1)).Trim())$Units"
    }
    Else { "OverRange" }
    return "$Digit$Suffix"
}

function Convert-kOrdinal
{
    param (
        [Parameter(ValueFromPipeline, Position = 0, Mandatory = $true)]
        [decimal]$Num,
        [Parameter(Position = 1, Mandatory = $false)]
        [int]$digits = 2,
        [Parameter(Position = 2, Mandatory = $false)]
        [string]$Units
    )
    
    if ($NUM -lt 1E+28)
    {
        [int]$Ordinal = ([math]::Floor((($Num.ToString()).Length - 1)/ 3))
        [string]$Digit = [math]::Round($Num / [math]::pow(1000, $Ordinal), $digits)
        [string]$Suffix = "$(((' KMGTPEZYB').Substring($Ordinal, 1)).Trim())$Units"
    }
    Else { "OverRange" }
    return "$Digit$Suffix"
}