Line 2: accept the date as a parameter and cast it to a date/time value, defaulting to today’s date if nothing is provided
Line 3: max sure we don’t think its Tuesday already
Line 5: starting on the first of each month, loop through the max number of days in the month
Line 8: if the date is Tuesday, add one to the counter
Line 9: once we find the second Tuesday
Line 10: add 4 more days to find the following Saturday and return the date text

You can take this function and do something creative, like find the next 5 years worth of patch Saturdays.

The most common exception I see happens when the data I’m storing in the hashtable is not unique. For example, in the first post in the series we created a simple hashtable from a list of HTML colors. If my input list had the color ‘red’ listed on two different lines, I would have seen an error similar to this:

Add : Exception calling “Add” with “2″ argument(s): “Item has already been added. Key in dictionary: ‘Red’ Key being
added: ‘Red’”
At line:1 char:17
+ $colorCodeHT.Add <<<< ('Red','123456')
+ CategoryInfo : NotSpecified: (:) [], MethodInvocationException
+ FullyQualifiedErrorId : DotNetMethodException

This is an easy error message to generate if you want to see the actual error. Follow the examples in the first post and then try and re-add the color red using the following line:

The hashtable object includes a .Contains method, which can be used in an if statement to prevent this exception from happening:

This statement checks for the presence of a ‘Red’ item and only attempts to add if a value does not already exist.

For purposes of sample data, create an array object of colors and HTML color codes.

Define a hashtable object:

Examples for adding to a hashtable:

Examples for updating existing entries

Examples for removing from a hashtable:

We can use Measure-Command to show how long each of these statements takes to execute. Here is a quick refresher on using Measure-Command to show how long it takes to execute a command…just replace “PUT EACH COMMAND HERE” with your actual command:

Using the examples from the previous post, we return Total Millisecond execution times of:

In this sample, returning a value from the hashtable (example 4) is 600 times faster than using the array object (example 2)! Just because this step was faster, it doesn’t mean hashtables are always best. If we take into account the overhead from creating the hashtable (add the execution times of example 3 and 4 together), then using the array object is actually more efficient. The performance gain is only noticeable if you plan to re-use the hashtable over several iterations.

Even though a hashtable requires a bit of setup, it becomes more efficient with repetitive use. The example with HTML color codes only has around 290 items in the hashtable. This performance improvement is more noticeable with larger hashtables, especially when they are used many times within the script.

A hashtable stores indexed key-value pairs in memory and is similar to the vbscript dictionary object. To help describe these concepts, I have listed a few examples based on a CSV file containing HTML color codes.

The examples below will:
1.) Import the CSV into a powershell array object,
2.) Show how to use the array object to return a specific code given a color name
3.) Convert the object from step 1 into a hashtable
4.) Show how to use the hashtable to return a specific code given a color name

All of the following examples will require a distinguishedName value in AD, so I will set a common variable here. You will need a valid distinguishedName defined in a varible like this if you want to follow along.

$distinguishedName = "CN=Brian Wuchner,OU=Test Users,DC=bwuch,DC=local"

The first test we will do is to update the displayName of the user. This is easy…we don’t care what the existing value is, we are just going to set it to whatever string value we want. We will do this by creating an object representing the Directory Entry of my user, updating the displayName attribute of that object and finally updating/committing that change back to the directory as follows.

That is a rather straight forward process. However, it becomes slightly more complex if we want to clear the attribute and make it null. One would think you could simply think you could set the displayName equal to $null using something like this:

However, if you try that you will most likely get a chance to see the following error message:

Exception setting "displayName": "Value cannot be null.

As a follow up, you might think “I’ll just set the attribute to an empty string” like this:

The only problem with that…setinfo will fail with the following error.

setinfo : Exception calling "setinfo" with "0" argument(s): "The attribute syntax specified to the directory service is invalid.

Does that mean its time to give up? Are we just going to have to live with bad data in AD? Never!

There are at least two ways to clean this up. The first way is my favorite (I’ve been using it since vbscript). You simply need to refer to the Microsoft article HOW TO: Use ADSI to Set LDAP Directory Attributes and you’ll realize this can be accomplished with PutEx.

In the above example, we use the constant ADS_PROPERTY_CLEAR by placing a ’1′ as the first argument in our method, then specifying the displayName as the attribute we want to clear, and finishing up by providing the desired value. Since we want the value to be clear, and we’ve already specified the ’1′ to clear, we just need to specify something so the method has enough parameters. I use 0 just for fun.

Another option is to call the Remove method and specify the value we want to remove. The downside is the attribute MUST have a value or you get an error when trying to clear it. We can overcome that with a simple if statement like this:

It doesn’t matter which of the options I use, the end result is the same — a clear attribute. I hope this post helps if you ever need to clear out an attribute.

NOTE: This function requires an additional function: Get-VIScheduledTasks to find the task by name. In addition the usage example below requires Get-VMScheduledSnapshots. Both functions are available here: New vCenter Scheduled Tasks with PowerCLI (Part 1).

Usage example:

# This example will find all VM Scheduled Snapshots which 
# are not scheduled to run again, then remove each one by name.
Get-VMScheduledSnapshots | 
?{$_.NextRunTime -eq $null} | %{ Remove-VIScheduledTask $_.Name }

NOTE: This function requires two additional functions, Get-VMScheduledSnapshots and Get-VIScheduledTasks, available here: New vCenter Scheduled Tasks with PowerCLI (Part 1).

# Create a snapshot of the VM test002 at 9:40AM on 3/2/13
New-VMScheduledSnapshot test002 "3/2/13 9:40AM"

# Create a snapshot and send an email notification
New-VMScheduledSnapshot test002 "3/2/13 9:40AM" myemail@mydomain.com

# Use all of the options and name the parameters
New-VMScheduledSnapshot -vmname 'test001' -runtime '3/2/13 9:40am' -notifyemail 'myemail@mydomain.com' -taskname 'My scheduled task of test001'

I hope someone finds this function useful.

The following two functions can be used to get information on Scheduled Tasks inside vCenter. The first function Get-VIScheduledTasks will simply return a list of all scheduled tasks that exist in a vCenter environment. I picked out a handful of properties that I figured would be needed and return those by default, casting the date/time values into local time. If you need all of the properties (the native .Net view of the Scheduled Task Info objects) you can include the parameter -Full and all of the properties will be returned.

This next function calls above function, but only returns the tasks whose action is “CreateSnapshot_Task”

Sample usage would be:

# To find all tasks that failed to execute last run
Get-VIScheduledTasks | ?{$_.State -ne 'success'}

# To find all snapshots that are not scheduled to run again:
Get-VMScheduledSnapshots | ?{$_.NextRunTime -eq $null}

I hope you find these functions useful. Be sure to check out the next post – on creating scheduled snapshots with PowerCLI!

Here is an example of how to get mailbox size for all users on the same Exchange server:

Get-MailboxStatistics -Server EXCHANGE01 | 
Select-Object -Property DisplayName, 
@{N="SizeMB";E={$_.TotalItemSize.Value.ToMB()}}, Identity | 
Export-Csv file2.csv -NoTypeInformation

The first thought that came to mind had involved Group-Object and Measure-Object. I threw something together that got the job done, but decided to clean it up a bit and thought I’d share it here.

Hope someone else finds this helpful!