Checking if PC exists in AD, and if not creating it - powershell

Question

Need to write a script to take an input file (text) list of names, check if it exists in AD, and create new computers.
The requirements are as follows -
Computer names are based on the users name (input from file)
Names must be 15 characters (for name resolution)
if the truncated name doesnt exist, create a computer object in specific OU with the truncated name.
If the truncated name does exist, append -# and test to see if it exists until it finds one that doesnt, then create new computer object with that name.
At the end I will need to output the results to an array but I haven't started adding that yet since this doesn't work.
So I finally got the "else" part but the if part at the beginning does not work.
$users = get-content C:\scriptdata\VMS.txt
$OU = ************
foreach ($user in $users)
{
$cleanname = if ($user.Length -gt 15) { $user.Substring(0, 15) } else { $user }
$exist = (get-adcomputer $cleanname) -eq $null
if ((get-adcomputer $cleanname) -like "get-adcomputer : Cannot find an object with identity")
{
New-ADComputer -Name $cleanname -Path "$OU" -SAMAccountName $cleanname -confirm
}
else
{
$count=0
DO{
$count++
$cleanname13 = if ($user.Length -gt 13) { $user.Substring(0, 13) } else { $cleanname }
$cleannamedash = $cleanname13 + '-' + "$count"
}
UNTIL ((get-adcomputer $cleannamedash | out-null) -eq $null)
New-ADComputer -Name $cleannamedash -Path "$OU" -SAMAccountName $cleannamedash -confirm
}
}
currently works for -# but not for those that dont exist at all.

Answer 1

Have a look at Naming conventions in Active Directory for computers, domains, sites, and OUs.
You'll find that there is more to a valid computer name than just the length.
Mind that the New-ADComputer cmdlet creates a new computer object, but does not join a computer to a domain.
Something like this should work (untested)
$computers = Get-Content C:\scriptdata\VMS.txt | Where-Object { $_ -match '\S'}
$OU = ************
foreach ($name in $computers) {
$newName = ($name -creplace '[\\/:*?"<>|.]','').Substring(0, 15)
try {
$computer = Get-ADComputer -Filter "Name -eq '$newName'" -PassThru -ErrorAction Stop
}
catch {
$computer = $null
}
if ($computer) {
# a computer with that name already exists, create a new name by adding a dash and two digit number
$count = 0
$name12 = $newName.Substring(0, 12) # we're going to add three characters
# get an array of computernames that are like the one you want to create
$existingComputers = Get-ADComputer -Filter "Name -like '$name12-*'" | Select-Object -ExpandProperty Name
do {
$newName = '{0}-{1:00}' -f $name12, ++$count
}
until ($existingComputers -notcontains $newName -or $count -gt 99)
if ($count -gt 99) {
$newName = '{0}-XX' -f $name12
throw "Cannot create computer $newName because all index numbers 00..99 are taken.."
}
}
# use splatting, because New-ADComputer has MANY parameters
$props = #{
'Name' = $newName
'Path' = $OU
'SamAccountName' = $newName
'Enabled' = $true
'Confirm' = $true
}
Write-Host "Creating computer '$newName'"
New-ADComputer #props
}

Answer 2

I assume you mean that this is the line that's not working:
if ((get-adcomputer $cleanname) -like "get-adcomputer : Cannot find an object with identity")
And even this doesn't work:
$exist = (get-adcomputer $cleanname) -eq $null
The reason is the same in both cases: If the computer doesn't exist, then Get-ADComputer throws an exception and the comparison is never done.
There is a good article about this here, but in short, the solution is to catch the exception. For you, it would look something like this:
try {
$computer = Get-ADComputer $cleanname
# If we get here, we know it exists
# You can put your loop here and just keep looping until Get-ADComputer throws an exception
}
catch [Microsoft.ActiveDirectory.Management.ADIdentityNotFoundException]
{
# Whatever you last tried doesn't exist. Create it here.
}