Powershell Script for Microsoft eBook Giveaway

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# Eric Ligmans Amazing Free Microsoft eBook Giveaway
# https://blogs.msdn.microsoft.com/mssmallbiz/2017/07/11/largest-free-microsoft-ebook-giveaway-im-giving-away-millions-of-free-microsoft-ebooks-again-including-windows-10-office-365-office-2016-power-bi-azure-windows-8-1-office-2013-sharepo/
# Link to download list of eBooks
# http://ligman.me/2tk1D2V
# Thanks David Crosby for the template (https://social.technet.microsoft.com/profile/david%20crosby/)
#
# Modified by Robert Cain (http://arcanecode.me)
# Added code to check to see if a book was already downloaded,
# and if so was it the correct file size. If so, the book
# download is skipped. This allows users to simply rerun the
# script if their download process is interrupted.
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# Set the folder where you want to save the books to
$dest = "C:\Book\" # Make sure the file path ends in a \

# Download the source list of books
$downLoadList = "http://ligman.me/2tk1D2V"
$bookList = Invoke-WebRequest $downLoadList

# Convert the list to an array
[string[]]$books = ""
$books = $bookList.Content.Split("`n")

# Remove the first line - it's not a book
$books = $books[1..($books.Length -1)]
$books # Here's the list

# Get the total number of books we need to download
$bookCount = $($books).Count

# Set a simple counter to let the user know what book
# number we're currently downloading
$currentBook = 0

# As an option, we can have it log progress to a file
$log = $true

if ($log -eq $true)

{

  # Construct a log file name based on the date that
  # we can save progress to
  $dlStart = Get-Date
  $dlStartDate = "$($dlStart.Year)-$($dlStart.Month)-$($dlStart.Day)"
  $dlStartTime = "$($dlStart.Hour)-$($dlStart.Minute)-$($dlStart.Second)"
  $logFile = "$($dest)BookDlLog-$dlStartDate-$dlStartTime.txt"

}

# Download the books
foreach ($book in $books)

{

  # Increment current book number
  $currentBook++
  try

  {

    # Grab the header with the books full info
    $hdr = Invoke-WebRequest $book -Method Head

    # Get the title of the book from the header then
    # make it a safe string (remove special characters)
    $title = $hdr.BaseResponse.ResponseUri.Segments[-1]
    $title = [uri]::UnescapeDataString($title)


    # Construct the path to save the file to
    $saveTo = $dest + $title

    # If the file doesn't exist, download it
    if ($(Test-Path $saveTo) -eq $false)

    {

      $msg = "Downloading book $currentBook of $bookCount - $title"
      $msg
      if ($log -eq $true) { "`n$($msg)" | Add-Content $logFile }
      Invoke-WebRequest $book -OutFile $saveTo

    }

    else

    {

      # If it does exist, we need to make sure it wasn't
      # a partial download. If the file size on the server
      # and the file size on local disk don't match,
      # redownload it

      # Get the size of the file from the download site
      $dlSize = $hdr.BaseResponse.ContentLength
      # Get the size of the file on disk
      $fileSize = $(Get-ChildItem $saveTo).Length

      if ($dlSize -ne $fileSize)

      {

        # If not equal we need to download the book again
        $msg = "Redownloading book $currentBook of $bookCount - $title"
        $msg
        if ($log -eq $true) { "`n$($msg)" | Add-Content $logFile }
        Invoke-WebRequest $book -OutFile $saveTo

      }

      else

      {

        # Otherwise we have a good copy of the book, just
        # let the user know we're skipping it.
        $msg = "Book $currentBook of $bookCount ($title) already exists, skipping it"
        $msg
        if ($log -eq $true) { "`n$($msg)" | Add-Content $logFile }

      }

    }

  } # end try

  catch

  {

    $msg = "There was an error downloading $title. You may wish to try to download this book manually."
    Write-Host $msg -ForegroundColor Red
    if ($log -eq $true) { "`n$($msg)" | Add-Content $logFile }

  } # end catch

} # end foreach


# Let user know we're done, and give a happy little beep
# in case they aren't looking at the screen.
"Done downloading all books"
[Console]::Beep(500,300)