Batch File: Delete Duplicate Files

Using this Batch File

Some time ago a friend of mine gave me a bunch of JPG files, but for some reason she had two copies of every image in the collection. The names of the images had all been randomized, and since there were hundreds of files in the collection it would have taken hours to find and delete the duplicates. With that in mind, I wrote the following batch file that loops through the collection of files and does a binary comparison to find and delete duplicate files.

To use the example code, copy the batch file code from below into Notepad and save it as "_del_dupes.cmd" in the folder where you have duplicate files

Note: As with many utilities that I write - this is a destructive operation, meaning that it will delete files without prompting, so you should always make a backup just in case something goes terribly wrong... ;-]

Batch File Example Code

@echo off

dir *.jpg /b > _del_dupes.1.txt

for /f "delims=|" %%a in (_del_dupes.1.txt) do (
   if exist "%%a" (
      dir *.jpg /b > _del_dupes.2.txt
      for /f "delims=|" %%b in (_del_dupes.2.txt) do (
         if not "%%a"=="%%b" (
            echo Comparing "%%a" to "%%b"...
            fc /b "%%a" "%%b">NUL
            if errorlevel 1 (
               echo DIFFERENT
            ) else (
               echo SAME
               del "%%b"

del _del_dupes.?.txt

FTP Clients - Part 4: FileZilla

For this next installment in my FTP Clients series, I'd like to take a look at the FileZilla FTP client. For this blog post I was using FileZilla version 3.1.6.

There are a lot of places where you can find FileZilla, but the best location is the official FileZilla web site at The FileZilla FTP client is free, so you can't beat the price. ;-]

The user interface is pretty straight-forward: you have separate windows for your local and remote files/folders, as well as a logging window that lists the FTP commands that are sent and the FTP server's responses.

FileZilla has a great Site Manager feature, which allows you to store commonly-used connections to FTP sites.

Using FTP over SSL (FTPS)

When creating a connection to an FTPS server, FileZilla has two options: FTPS and FTPES. It's important to have this option configured correctly, otherwise you will run into problems when trying access a site using FTPS. If you'll recall from my "FTP Clients - Part 2: Explicit FTPS versus Implicit FTPS" blog post, Explicit FTPS allows the client to initiate SSL/TLS whenever it wants, but for most FTP clients that will be when logging in to your FTP site, and in that regard it may almost seem like Implicit FTPS, but behind the scenes the FTP client and server are communicating differently.

In the case of FTP7, the following rules apply:

  • If you enable FTPS and you assign the FTP site to port 990, you are using Implicit SSL - FileZilla refers to this as FTPS.
  • If you enable FTPS and you assign the FTP site to any port other than port 990, you are using Explicit SSL - FileZilla refers to this as FTPES.

Using FTP Virtual Hosts

Because FileZilla's site manager allows you to specify the virtual host name as part of the user credentials, FileZilla works great with FTP7's virtual host names. All that you need to do is use the "|username" syntax when specifying your username, and when you connect to the FTP7 server it will route your requests to the correct FTP virtual host site.

Unfortunately, even though FileZilla allows you to send custom commands, you cannot send custom commands outside of an established FTP session, so you can't send the FTP HOST command as part of your login, therefore true FTP hosts are not supported.

Directory Browsing

Using MS-DOS or UNIX directory listings in FTP7 didn't have any impact on whether FileZilla could render directory listings, nor did configuring any of the other options such as four-digit years, etc. When I create FTP connections in FileZilla's site manager it defaults to auto-detecting the FTP server type, which makes the directory browsing behavior transparent to the client. (Behind the scenes FileZilla is sending an FTP SYST command, which allows FileZilla to detect the operating system.)

You can customize the server type in the advanced settings for your FTP connection, so you can match up your FTP7 directory listing options and the server type that FileZilla expects, but personally I have had no problems with auto-detection so I prefer to use that option.

On a side note, if you intentionally misconfigure FileZilla's server type settings, you can cause FileZilla to behave strangely. For example, choosing a VMS server type and configuring FTP7 to use MS-DOS directory listings will not work, but then again - I wouldn't expect that to work. ;-]

Scorecard for FileZilla

So - that concludes our quick round-trip for some of FileZilla's features, and here's the scorecard results:

Client NameDirectory
FileZilla 3.1.6 Rich Y Y Y N

Note: As with all of the FTP clients in this blog series, there are a great number of additional features that FileZilla provides - I'm just keeping the focus on a few specific topic areas that apply to FTP7.

Note: This blog was originally posted at

FTP Clients - Part 3: Creating a Global Listener FTP Site

In my "FTP Clients - Part 1: Web Browser Support" blog post, I mentioned creating a secured Global Listener FTP Site when you're working with FTP virtual hosts, but I didn't really explain what I meant by that or why you would want to do this. With that in mind, today's blog post is to describe how and why you might want to create a Global Listener FTP Site.

To start things off, the concept is really simple - a Global Listener FTP Site is an FTP site with no virtual host binding and anonymous access disabled. It's kind of like having a "Default FTP Site" with restricted access. Here's why this is a good idea when you're working with FTP virtual hosts - some clients default to anonymous, like web browsers, and if anonymous succeeds then the FTP client doesn't have the opportunity to enter the FTP virtual host name, so you can't get to the virtual host site.

To refresh everyone's memory, there are two different methods for binding multiple FTP host names to IP addresses in FTP7:

  • FTP Virtual Host Names - This uses the "|username" syntax as part of the client login in order to route FTP requests to the correct FTP site. This syntax is compatible with FTP almost every FTP clients, and should be thought of as a backwards-compatible method for binding multiple FTP host names to a single IP address.
  • FTP True Host Names - This uses the FTP HOST command, which is still only an IETF draft at the moment. In the future this may be the way that FTP clients and servers automatically communicate with each other, like the "Host:" header does for HTTP, but that may still have a few years at the very least.

Unless your FTP client allows sending custom FTP commands, you won't be able to use FTP True Host Names, so if you want to host several FTP sites on the same IP address then your only option is to use FTP Virtual Host Names. The trouble is, as I mentioned earlier, that some FTP clients (like web browsers) try to log in using anonymous first. If all of your FTP sites are bound to a virtual host name, the FTP client will get a "550-No such host is known" error from the FTP server, because the anonymous user did not specify a virtual host name as part of the USER command. On some clients you could fix that by specifying "|anonymous" as your anonymous user name, but in most cases the login attempt will just fail.

If you create an FTP site that has no virtual host name, then the FTP service will have some place to send these default anonymous requests. When this FTP site does not have anonymous access enabled, the client will be prompted for their username, which will allow you to enter the "|username" syntax to specify the virtual host name.

Please note that creating a Global Listener FTP site is really more of a workaround for the way that some FTP clients behave - it's certainly not required, and it only applies to situations where you are using FTP Virtual Host Names. For example, if you are using user isolation to restrict users to specific paths on a single FTP site, the Global Listener FTP site would be completely unnecessary.

More Information

Note: See my Virtual Hosts and Host Names in FTP7 blog post for more information about FTP Virtual Host Names and FTP True Host Names, and see for more information about status of the FTP HOST command.

Note: This blog was originally posted at