BSonPoSH

Earlier this month I had a discussion with Laura (of AD Cookbook fame) regarding ADLDS and how to test convergence. After a few minutes I remembered I had a AD convergence script I wrote a while back found HERE. With a little tweaking (specifically discoverability) we converted it to test ADLDS as well. Below you will fine the result.

Parameters
- Server: The ADLDS/ADAM server that hosts the application partition you want to test
- DN: The distinguished name of the application partition you want to test (will try to discover)
- Port: Port ADLDS/ADAM list on (Default 389)
- Table [switch]: A switch that outputs an object with the results.

Note: Please feel free to provide any feedback you have regarding this. I do not use ADLDS or ADAM so other than my test environment I really cannot play with this.

The Code
Test-LDSReplication.ps1

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tshell :: Jan.26.2009 :: Active Directory, All, Powershell :: No Comments »

A problem come that required me to check the routing table on a large number of machines. My first thought was to try to find a .NET class to dump the table, but alas I could not find any class to do what I wanted. That was a bummer but not unexpected so I decided to just use ol’faithful psexec.exe (Found here.)

Now, for those of you that have used ‘route print’ before you know the output is well… verbose and clearly that would not be very helpful for filtering.

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Enter ‘Get-RouteTable” (found below)

I share this, not so much because I found it incredibly useful (although I did,) but because it illustrates what I have found to be a great way of creating complex Regular Expressions (for the sake of brevity I will use RegEX for the rest of the article.)

My approach is quiet simple. Create a string object for the RegEx and build the Regex over time testing each section.

Lets take this string for example

Active Routes:
Network Destination        Netmask                 Gateway          Interface            Metric
          0.0.0.0                   0.0.0.0                    192.168.1.1     192.168.1.13     25
        127.0.0.0                 255.0.0.0                127.0.0.1          127.0.0.1           306
        127.0.0.1                 255.255.255.255    127.0.0.1           127.0.0.1           306

I wanted to extract the Network Destination, Netmask, Gateway, Interface, and Metric and make them properties on a custom object. How does one go about that? One way is to create a regular expression with labels and use $matches to extract the information. This is route I took, but instead of trying to write a single complex RegEx and then trouble-shooting it for hours I decided to break down the regular expression into bite size chunks.

To show you what I mean by complex… here is the RegEx you end up with

“^\s+(?<Network>\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})\s+(?<NetMask>\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})\s+(?<Gateway>\d{1,3
}\.\d{1,3}\.\d{1,3}\.\d{1,3})\s+(?<Interface>\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})\s+(?<Metric>\d{1,4})$”

As you can this is fairly complex and could be a HUGE pain to trouble shoot.

Following my approach you break down. First you add the begin and end to the regex

$DiscoverRoute  = “^\s+”

$DiscoverRoute += “.+$”

The next step is we add a label and pattern for the “Network Destination” and test

$DiscoverRoute  = “^\s+”

$DiscoverRoute += “(?<Network>\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})\s+”

$DiscoverRoute += “.+$”

(route print) | ?{$_ -match $DiscoverRoute}

If you get results you expect the next step is to make sure $matches sees the labels as you expect

(route print) | ?{$_ -match $DiscoverRoute} | %{$matches}

Great! Now we can the next part

$DiscoverRoute  = “^\s+”
$DiscoverRoute += “(?<Network>\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})\s+”
$DiscoverRoute += “(?<NetMask>\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})\s+”
$DiscoverRoute += “.+$”

Repeat the Last test but make sure you have a value for both Network and NetMask

(route print) | ?{$_ -match $DiscoverRoute} | %{$matches}

Rinse and repeat until you end up with this

$DiscoverRoute  = “^\s+”
$DiscoverRoute += “(?<Network>\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})\s+”
$DiscoverRoute += “(?<NetMask>\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})\s+”
$DiscoverRoute += “(?<Gateway>\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})\s+”
$DiscoverRoute += “(?<Interface>\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})\s+”
$DiscoverRoute += “(?<Metric>\d{1,4})”
$DiscoverRoute += “.+$”

This does not work just yet… can you spot why? The reason is because we have been adding “.+$” (zero or more of anything) to the end every time for testing purposes. We now need to remove this and add the $ to the end of the Metric string because the EOL is immediately after the last digit in Metric column. We end up with this

$DiscoverRoute  = “^\s+”
$DiscoverRoute += “(?<Network>\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})\s+”
$DiscoverRoute += “(?<NetMask>\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})\s+”
$DiscoverRoute += “(?<Gateway>\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})\s+”
$DiscoverRoute += “(?<Interface>\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})\s+”
$DiscoverRoute += “(?<Metric>\d{1,4})$”

We took a complex RegEx and with a little string concantination we were able to break it down and make the task quite simple.

Note: Another cool effect of this method is that we can easily comment out a section that maybe break the entire regular expression like this

$DiscoverRoute  = “^\s+”
$DiscoverRoute += “(?<Network>\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})\s+”
$DiscoverRoute += “(?<NetMask>\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})\s+”
#$DiscoverRoute += “(?<Gateway>\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})\s+”
$DiscoverRoute += “.+(?<Interface>\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})\s+”
$DiscoverRoute += “(?<Metric>\d{1,4})$”

Just make sure that you add the “.+” to the line just after the comment line. This allows the regular expression to replace that section with basically anything.

NOTE: A final, slightly embarrassing, note. After writing the script below I realized this information (save the persistent routes) is readily available using WMI via the Win32_IP4RouteTable class.

The Code:

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tshell :: Jan.16.2009 :: All :: No Comments »

One of the most useful tools a scripter has at their disposal is Regular Expressions. The problem is that regular expressions can seem like Greek and for most folks learning them can seem an impossible task. I hope this blog post provides those people some hope as well as some tools they can use to tackle this mountain one foot at a time.

NOTE: I would like to make this blog entry as dynamic as possible, so if you have your own tips… let me know and I will add them.

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Everyone is different, but this is how I went about learning Regular Expressions

• Phase one: Learn EXACTLY what a regular expression is and what it can and can NOT do.
• Phase two: Learn the syntax. I printed out the RegEx Cheet Sheet and use it daily.
• Phase three: Find a purpose. I find if I actually have a problem I spend more energy on learning.
• Phase four: Create a simple Regular Expression.
• Phase five: Build on your Regular Expression.
• Phase six: Trouble shooting the Regular Expression.

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Useful Tips:

• First things first… Click here and watch the vids
• Keep a cheat sheet close at hand!
• Take them in small bites. I hope to blog in detail about this later, but lets just say string concatenation is your friend
• Keep it simple!
• $matches is your friend! $matches is an object that Powershell creates when you make a RegEx call (like -match.)
• Google It. Chances are there is Regex already out there for what you need.
• Using Lables can save you time by extracting certain data and making it a property on $matches.
• RichardP from IRC says “Dont eat yellow snow?” Apparently he has experience in this area.

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Online Vids:
This is GREAT stuff provided by Shay (aka scriptfanatic)

Good Blog Entries:
MoW at it again.

References:
RegEx Cheet Sheet (my Favorite)
Regular-Expressions.info
Regular Expression Library

Online Regex Checkers:
RegEx Tester (my Favorite)
Regular Expression Library Tester

Books:
Mastering Regular Expressions (my Favorite)
Regular Expression Recipes for Windows Developers

Tools:
Expresso
RegEx Buddy

tshell :: Jan.11.2009 :: All :: 1 Comment »

Login… download… enjoy!

This is includes Powershell v2 (later build than CTP3) installed by default!

tshell :: Jan.08.2009 :: All :: No Comments »