Azure Powershell Question for Virtual Machine - azure

Question

I am reviewing a script that is supposed to delete a vm along with all of the resources attributed to the vm
Write-Host -NoNewline -ForegroundColor Green "Please enter the VM name you would like to remove:"
$VMName = Read-Host
$vm = Get-AzVm -Name $VMName
if ($vm) {
$RGName=$vm.ResourceGroupName
Write-Host -ForegroundColor Cyan 'Resource Group Name is identified as-' $RGName
#boot diagnostics container auto generated in storage account. Auto delete this storageURI property
$diagSa = [regex]::match($vm.DiagnosticsProfile.bootDiagnostics.storageUri, '^http[s]?://(.+?)\.').groups[1].value
Write-Host -ForegroundColor Cyan 'Marking Disks for deletion...'
$tags = #{"VMName"=$VMName; "Delete Ready"="Yes"}
$osDiskName = $vm.StorageProfile.OSDisk.Name
$datadisks = $vm.StorageProfile.DataDisks
$ResourceID = (Get-Azdisk -Name $osDiskName).id
New-AzTag -ResourceId $ResourceID -Tag $tags | Out-Null
if ($vm.StorageProfile.DataDisks.Count -gt 0) {
foreach ($datadisks in $vm.StorageProfile.DataDisks){
$datadiskname=$datadisks.name
$ResourceID = (Get-Azdisk -Name $datadiskname).id
New-AzTag -ResourceId $ResourceID -Tag $tags | Out-Null
}
}
if ($vm.Name.Length -gt 9){
$i = 9
}
else
{
$i = $vm.Name.Length - 1
}
$azResourceParams = #{
'ResourceName' = $VMName
'ResourceType' = 'Microsoft.Compute/virtualMachines'
'ResourceGroupName' = $RGName
}
$vmResource = Get-AzResource #azResourceParams
$vmId = $vmResource.Properties.VmId
$diagContainerName = ('bootdiagnostics-{0}-{1}' -f $vm.Name.ToLower().Substring(0, $i), $vmId)
$diagSaRg = (Get-AzStorageAccount | where { $_.StorageAccountName -eq $diagSa }).ResourceGroupName
$saParams = #{
'ResourceGroupName' = $diagSaRg
'Name' = $diagSa
}
Write-Host -ForegroundColor Cyan 'Removing Boot Diagnostic disk..'
if ($diagSa){
Get-AzStorageAccount #saParams | Get-AzStorageContainer | where {$_.Name-eq $diagContainerName} | Remove-AzStorageContainer -Force
}
else {
Write-Host -ForegroundColor Green "No Boot Diagnostics Disk found attached to the VM!"
}
Write-Host -ForegroundColor Cyan 'Removing Virtual Machine-' $VMName 'in Resource Group-'$RGName '...'
$null = $vm | Remove-AzVM -Force
Write-Host -ForegroundColor Cyan 'Removing Network Interface Cards, Public IP Address(s) used by the VM...'
foreach($nicUri in $vm.NetworkProfile.NetworkInterfaces.Id) {
$nic = Get-AzNetworkInterface -ResourceGroupName $vm.ResourceGroupName -Name $nicUri.Split('/')[-1]
Remove-AzNetworkInterface -Name $nic.Name -ResourceGroupName $vm.ResourceGroupName -Force
foreach($ipConfig in $nic.IpConfigurations) {
if($ipConfig.PublicIpAddress -ne $null){
Remove-AzPublicIpAddress -ResourceGroupName $vm.ResourceGroupName -Name $ipConfig.PublicIpAddress.Id.Split('/')[-1] -Force
}
}
}
Write-Host -ForegroundColor Cyan 'Removing OS disk and Data Disk(s) used by the VM..'
Get-AzResource -tag $tags | where{$_.resourcegroupname -eq $RGName}| Remove-AzResource -force | Out-Null
Write-Host -ForegroundColor Green 'Azure Virtual Machine-' $VMName 'and all the resources associated with the VM were removed sucessfully...'
}
else{
Write-Host -ForegroundColor Red "The VM name entered doesn't exist in your connected Azure Tenant! Kindly check the name entered and restart the script with correct VM name..."
}
I had a question: what does this block of code exactly do:
$diagSa = [regex]::match($vm.DiagnosticsProfile.bootDiagnostics.storageUri, '^http[s]?://(.+?)\.').groups[1].value
I know it matches the storage uri, but how? And why is this needed? I am not sure what the .groups[1].value is referring to either

Answer 1

$diagSa =
[regex]::match($vm.DiagnosticsProfile.bootDiagnostics.storageUri,
'^http[s]?://(.+?).').groups[1].value
I know it matches the storage uri, but how?
You are using the [regex] type accelerator & match method () in the above expression.
The Match() method is a way to instruct PowerShell to attempt to match a string inside of another string. The Match() method has two parameters; the string you'd like to match on and the regular expression you'd like to test against.
Whenever a match is found and a regex group is used; (), the [regex] type accelerator has a Captures property. This Captures property then has a property called Groups. This is a collection that contains lots of attributes of what was matched. The second element in that collection contains the actual value that was matched.
what the .groups[1].value is referring to either
groups[1].values returns the storage account name where the boot diagnostics container resides.
And why is this needed?
When creating an Azure VM, you always have the option of creating a boot diagnostics container. This is useful to troubleshooting VM boot issues but doesn’t get removed when a VM is deleted. Let’s remedy that.
To remove the boot diagnostics container, you first need to figure out the name of the storage account the container resides on. To find that storage account, you’ll have to do some parsing of the storageUri property that’s exists in the DiagnosticsProfile object on the VM.
for more information about [regex]::match().group[1].value expression refer the below blog :
https://mcpmag.com/articles/2015/09/30/regex-groups-with-powershell.aspx