Update an existing file - see comments

UpdateFile.ps1

# This script assumes it is being run from powershell "run as administrator" prompt.
#
# The script will check if it has already been run (FileBackupTo already exists),
# otherwise it will backup the target FileToUpdate and replace it with the $NewFile.
# It sets the updated file to "read only"

# The following paths must be updated as needed: 
# The current assumption is $NewFile is in the same directory as this script,

$FileToUpdate = "C:\Program Files\ATT Metrology\LTASWpf\LTAS30Block20.xit64"
$FileBackupTo = "C:\Program Files\ATT Metrology\LTASWpf\LTAS30Block20.xit64.old2021FrameUpdate"
$NewFile = ".\LTAS30Block20.xit64"

function updateFile()
{
    if (-not(Test-Path -Path $FileBackupTo -PathType Leaf)) {
         try {
             Write-Host "Backing up and updating [$FileToUpdate] template..."
             Rename-Item -Path $FileToUpdate -NewName $FileBackupTo
             Copy-Item $NewFile -Destination $FileToUpdate
             $status = Get-ChildItem $FileToUpdate
             $status.set_isreadonly($true)
         }
         catch {
             throw $_.Exception.Message
         }
     }
     else {
         Write-Host "Aborting. [$FileBackupTo] backup already exists."
     }
}

updateFile