The Surly Admin

Scan a Folder For Changes

Another fun little project popped up at Spiceworks yesterday.  OP (Original Poster) was looking to create a vbScript that would scan a folder for new files.  The Folder was actually part of an FTP site he had setup and he wanted to be notified by email whenever something new was uploaded to it.  Here’s how I went after the script.

So how do you figure out new files have been uploaded into a Folder?  There are a few things you can do.  One is you can save all of the filenames into a database/text file, then compare that file to what’s actually in the folder, if there’s a difference you have a hit!  Another method is you can use Windows event handling and actually trigger the script whenever there is a change.  But there is another way that turns out to be the easiest.  The script runs every 10 minutes, so we could do a simple search for files that have been updated in the past 10 minutes.  If we get a hit we get notified.  Now, you could edit a file and trigger the script too but in this case I believe that’s acceptable.

Turns out the actual code to detect a changed file in the past 10 minutes is pretty easy:

Get-ChildItem * | where ( $_.LastWriteTime -ge [datetime]::Now.AddMinutes(-10) }

You use Get-ChildItem to scan for all files in the folder you want (if you want to scan sub-folders too you would add the -recurse parameter) then pipe it into the Where cmdlet where you check the .LastWriteTime with the time right now minus 10 minutes.

Ryan Witschger made a great comment in his blog about declaring all of his variable as Parameters, which is a great idea.  By doing that it allows you to really make your script flexible as you can change these values on the fly and even run your script in multiple ways without changing code.  If you’ve ever had a script that you run for different things and then have to update that script “x” times because you made an update to it you know what I mean!  So on this script let’s declare some variables.

Param (
 [string]$Path = "D:\FTPSites\",
 [string]$SMTPServer = "smtpservername",
 [string]$From = "SFTPAlert@domain.com",
 [string]$To = "user@domain.com",
 [string]$Subject = "New File Uploaded to FTP Site"
 )

Since we’re sending an email we want to use the Send-MailMessage cmdlet to accomplish that.  Now, you could just run it with every property you need and the variables you’ve declared above but honestly it makes for pretty ugly looking code.  A nice workaround for that is a method called “splatting“.  In a nutshell you create a hash table with all of the properties you want to use, then when you call the Send-MailMessage cmdlet you use your hash table with a “@” symbol and that will apply the table as your properties.  Here’s how:

$SMTPMessage = @{
To = $To
From = $From
Subject = "$Subject at $Path"
Smtpserver = $SMTPServer
}
Send-MailMessage @SMTPMessage

Notice the Subject line?  I love the fact that in Powershell you don’t have to break out of a string to add variables within the text.  Such a time saver!

Now we’ve got all of our files located (if any), we’ve got the header information for our Send-MailMessage cmdlet, we just need the body.  For me, looks are everything so let’s have the script notify you that not only have files been uploaded, but which ones.  You’ll notice some odd code in the string declarations: “`n“.   The back tick character is the Powershell escape character, this allows you to put in reserved characters like the $ sign or the hash simple # in a string (which Powershell will try to interpret as a variable or comment) or you can also add special characters.  `n is a carriage return or new line.

If ($File)
{ $SMTPBody = "`nThe following files have recently been uploaded to your FTP site:`n`n"
$File | ForEach { $SMTPBody += "$($_.FullName)`n" }

We start by assigning a variable some simple information about what’s happened, then loop through all of the objects in $File and put the FullName property–which is the full path of the file.

And there you have it.  Create a scheduled task and run Powershell.exe as your program, and the following as the argument:

-ExecutionPolicy Bypass <pathtoscript>\Scan-FolderForFiles.ps1

You’ve also decided that you want to scan a folder on the file server called Suggestion Box and anytime someone places a file in there to email HR.  Schedule another task (doesn’t have to be on the file server) with these parameters:

<pathtoscript>\Scan-FolderForFiles.ps1 -Path "\\<fileserver>\<share>\Suggestion Box" -From SuggestionBox@domain.com -Subject "New File in Suggestion Box" -To HR@domain.com

This will override the Path, From, To and Subject fields while leaving the SMTPServer (your SMTP relay) field alone.

Here’s the full code with a little change to make some of the messaging more generic:

Param (
[string]$Path = "D:\FTPSites\",
[string]$SMTPServer = "smtpservername",
[string]$From = "SFTPAlert@domain.com",
[string]$To = "user@domain.com",
[string]$Subject = "New File Uploaded to FTP Site"
)

$SMTPMessage = @{
To = $To
From = $From
Subject = "$Subject at $Path"
Smtpserver = $SMTPServer
}

$File = Get-ChildItem $Path | Where { $_.LastWriteTime -ge [datetime]::Now.AddMinutes(-10) }
If ($File)
{ $SMTPBody = "`nThe following files have recently been added/changed:`n`n"
$File | ForEach { $SMTPBody += "$($_.FullName)`n" }
Send-MailMessage @SMTPMessage -Body $SMTPBody
}

September 11, 2012 - Posted by Martin9700 | PowerShell | Get-ChildItem, scan for changed files, scan for new files, Send-MailMessage, splat, splatting