Trying to Acquire 'tail' Result on Log Files of ESX Hosts Cluster-wide

[Butcha]

Good Afternoon everyone!!!

I am attempting to devise a script that I can use to point to clusters of ESX hosts and generate the last 10 lines of any particular log files on these systems using Get-log. First, I would like to point out that the following code works for one individual host:

$esx = Get-VMHost -VMhost "hostname"

$esxlog = Get-Log -Key "vmkernel" -VMHost $esx

$esxlog.Entries <----

---

I had to leave out the expression that specifies the last ten lines of $esxlog.Entries b/c this editor kept interpreting that part as html and presenting it as such

This will show expected results, which is the last 10 lines of the log on that host.

Now, when I try to expand upon this concept and try to create a loop based on this using the code below:

$esx = Get-Cluster "clustername" | Get-VMHost

foreach ($_ in $esx) {$esxlog = Get-Log -Key "vmkernel" -VMHost $_

$esxlog.Entries} <----

---

once again the code specifying the last ten lines has been omitted here for the sake of avoiding confusion

I only get the following error: A parameter cannot be found that matches parameter name 'System.Object[]'.

What am I doing wrong with my script?

[LucD · Accepted solution]

The variable $_ is a pre-defined variable so you shouldn't use it as your loop variable.

You could do it like this

$esx = Get-Cluster <clustername> | Get-VMHost
$esx | %{
	$esxlog = Get-Log -Key "vmkernel" -VMHost $_
	$nrEntries = $esxlog.Entries.Count
	Write-Host $_.Name -foregroundcolor green
	$esxlog.Entries[http://($nrEntries-11)..($nrEntries-1)|http://($nrEntries-11)..($nrEntries-1)]
}

[Butcha]

LucD, your suggestion worked flawlessly.........I appreciate your input.....if you dont mind, I'd love it if you could break your script down for me just a bit so that I can understand the logic behind how you decided to proceed.

[LucD]

Sure, no problem.

In variable $esx I get all the ESX servers that are in the cluster .

Provided you have more than 1 ESX server in the cluster, $esx will be an array of objects.

Them I pipe the contents of the array to the Foreach-Object cmdlet.

I used "%" but that is an alias for the Foreach-Object cmdlet.

By doing it this way I don't have to use a test to check if $esx is a single object (an atom) or an array of objects.

The pipe takes care of that.

In the codeblock of the Foreach-Object the current object, which represents an ESX server object, is passed in the variable $_.

From there it is rather straightforward:

• get the content of the vmkernel log into variable $esxlog

• in that variable, which is again an object, there is a property "Entries" which contains an array of strings, with 1 line of the log per element

• as with each array you can find the number of elements in the array with the Count property

• I write the name of the server (in green) to the console

• I display the last 10 lines of the log

Feel free to ask further questions if something is not yet clear.

[Butcha]

LucD,

Great info! I appreciate your time!

Two things stick out in my mind:

#1: How do I find a comprehensive definition of the various object types and their properties and methods? I understand the get-member cmdlet, but what if one ddnt know what even exists?

#2: The part where u are specifying exactly what range of lines of the log file to display, what is the significance of the '-11......-1'? What is the relationship with this range identifier and the retrieval of the 'count' property?

[LucD]

#1: if you mean the objects that come with the VITK I'm afraid that you will have to use the Get-Member cmdlet.

Hal's soon to be released book will contain a wealth of information on the VITK objects.

As a side remark, the objects as used by the VITK are not the objects that the VI API uses !

#2: The number of elements (lines from the log) in the Entries property is not always the same.

To get the number of elements I store the Count property in variable $nrEntries.

To get the last 10 lines from the log and taking into account that an array index starts at 0 (zero), I start at the 10th line before the end.

And a..b is a PowerShell feature that allows you to address a series of elements in an array.

Example:

- Get-VIEvent returned 88 lines

- $nrEntries will contain the value 88

- I ask for the array elements 88-11 till 88-1 ==> 77 till 87 ==> the last 10 lines

[halr9000]

Just to assist in future Googling, "a..b" is called the range operator.

[PowerShell MVP|https://mvp.support.microsoft.com/profile=5547F213-A069-45F8-B5D1-17E5BD3F362F], VI Toolkit forum moderator

Author of the upcoming book: Managing VMware Infrastructure with PowerShell

Co-Host, PowerScripting Podcast (http://powerscripting.net)

Need general, non-VMware-related PowerShell Help? Try the forums at PowerShellCommunity.org

[Butcha]

Great Great info, LucD and Halr9000!!!

I have learned a great deal from this discussion, as focused as it was.......Hal, I cant wait for your book man!