Creating variables and prompts depending using for loop depending on user input

Question

I am making a user input driven deployment script. Basically I am asking a user "How many VM's would you like to deploy" and depending on the answer I want to create and use so many variables.

So my code currently asks the user for number of VM's Then it loops to create a new variable and ask user to fill that variable however I don't know how to use the variable that is created.

$Vmnumber = Read-Host "Enter number iof VM's that you would like to create."
for($i = 1; $i -le $Vmnumber; $i++){
    New-Variable -Name "vmip$i"
    Write-Host "Please Enter IP Address for VM$i (Site A): " -ForegroundColor Yellow -NoNewline

    do {
        if(($vmip + $i = Read-Host "Press enter to accept default IP form PHPIPAM" $SiteAsorting[$i]"or type a differnet one.") -eq ''){$vmip + $i = $SiteAsorting[$1]}else{$vmip + $i}
        $ok = $vmip + $1 -match $IPPattern
        if ($ok -eq $false) {
            Write-Warning ("'{0}' is not an IP address." -f $vmip + $i)
            write-host -fore Yellow "Please Enter IP for VM$i : " -NoNewline
        }
    } until ( $ok )

}

'''

I would like the the code to create new variable and ask for user input every iteration.

Thanks in advance for any help

I usually don't recommend Read-Host because it can't be automated. I would instead recommend to use command-line parameters (param() statement). Your script will be much more flexible, and you can have input validation more or less for free. — Bill_Stewart
– Bill_Stewart, Commented Aug 27, 2019 at 16:26
Your use of dynamically named variables is completely unnecessary here - I'd strongly recommend re-using a local variable (ie. just $vmip), and then add the final value to an array, list or hashtable — Mathias R. Jessen
– Mathias R. Jessen, Commented Aug 27, 2019 at 16:29
please pay attention to what Mathias R. Jessen said about dynamically named $Vars ... don't do that. [grin] seriously, it is a really bad idea when there are structures already available to do what you want ... arrays, generic.lists, and lots of other collection types. — Lee_Dailey
– Lee_Dailey, Commented Aug 27, 2019 at 16:51
@MathiasR.Jessen Thanks for that. How would I go about that in my example? — Robert Rozek
– Robert Rozek, Commented Aug 28, 2019 at 8:25

Mathias R. Jessen · Accepted Answer · 2020-04-27 16:07:00Z

2

I don't know how to use the variable that is created.

That makes sense, and the solution is simple:

Don't use dynamically named variables.

Use an array or a dictionary/hashtable instead! Since in your example you want to name the VM's starting from 1, and array indices start at 0, let's use a hashtable instead:

# First, let's ensure no one enters a nonsensical value like "100000" or "-3" or "ur mom"
while(([int]$numberOfVMs = Read-Host "Enter number of VM's that you would like to create.") -notin 1..20){
    Write-Error "Please enter a number between 1 and 20"
}

# Create a hashtable to hold the IP addresses
$VMIPs = @{}

foreach($VMNumber in 1..$numberOfVMs){
    do {
        Write-Host "Please Enter IP Address for VM${VMNumber} (Site A): " -ForegroundColor Magenta -NoNewline

        # Read whatever the user suggests
        $suggestedIP = Read-Host "Press enter to accept default IP form PHPIPAM ($($SiteAsorting[$VMNumber]) or type a differnet one."

        # Handle the default 
        if ($suggestedIP -eq '') {
            $suggestedIP = $SiteAsorting[$VMNumber]
        }

        # Now, let's do our validation on the IP (regex is a poor validation tool here, but you can update this later)
        $ok = $suggestedIP -match $IPPattern

        if (-not $ok) {
            # Warn the user that the IP wasn't valid
            Write-Warning "${suggestedIP} is not a valid IP address!"
        }
        else {
            # or, store the IP for later reference
            $VMIPs["VM${VMNumber}"] = $suggestedIP
        }
    } until ( $ok )
}

Notice the string value we used for the hashtable keys above: "VM${VMNumber}" - so, now, if I entered 3 in the first prompt, we should expect a hashtable with the keys VM1, VM2 and VM3, so later we can do:

foreach($VMNumber in 1..$numberOfVMs){
    Write-Host "Now assigning IP to VM${VMNumber}!"
    $IPAddress = $VMIPs["VM${VMNumber}"]
    Add-VMIPAddress -VM "someVMName" -IP $IPAddress
}

edited Apr 27, 2020 at 16:07

answered Aug 28, 2019 at 20:46

Mathias R. Jessen

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2 Comments

Robert Rozek Over a year ago

Thank you very much for explaining, and giving examples. I shall give that a go!

Robert Rozek Over a year ago

This has worked like charm. I accept this as a valid response and thank you for explanation. This helped me to understand the proper way. I feel comfortable to reuse that code in other parts of my script !

Mahmood Shehab · Accepted Answer · 2019-08-27 20:33:59Z

0

do {
Write-Host " Enter number of VM's that you would like to create. " -NoNewline ;
write-host "[VMs] : " -ForegroundColor Yellow -NoNewline;
    $NumberOfVM = "Notok"; $NumberOfVM = Read-Host; 
    if($NumberOfVM-ne $Null -and $NumberOfVM.Length -le 30 -$NumberOfVM)
    {Write-Host "ok" -NoNewline}else{Write-Host "Are You Kidding Me?!" -F Red -B Yellow}} 
until($NumberOfVM -eq "ok")

answered Aug 27, 2019 at 20:33

Mahmood Shehab

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Creating variables and prompts depending using for loop depending on user input

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Don't use dynamically named variables.

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Don't use dynamically named variables.

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