<p>I sometimes use the feature 'Reconcile Offline Work...' found in Perforce's P4V IDE to sync up any files that I have been working on while disconnected from the P4 depot. It launches another window that performs a 'Folder Diff'.</p>

<p>I have files I never want to check in to source control (like ones found in bin folder such as DLLs, code generated output, etc.) Is there a way to filter those files/folders out from appearing as "new" that might be added. They tend to clutter up the list of files that I am actually interested in.  Does P4 have the equivalent of Subversion's 'ignore file' feature? </p>

As of version 2012.1, Perforce supports the
```
P4IGNORE
```
environment variable. I updated my answer to
this question about ignoring directories
with an explanation of how it works. Then I noticed this answer, which is now superfluous I guess.
Assuming you have a client named "CLIENT", a directory named "foo" (located at your project root), and you wish to ignore all .dll files in that directory tree, you can add the following lines to your workspace view to accomplish this:
```
-//depot/foo/*.dll //CLIENT/foo/*.dll
-//depot/foo/.../*.dll //CLIENT/foo/.../*.dll
```
The first line removes them from the directory "foo" and the second line removes them from all sub directories.  Now, when you 'Reconcile Offline Work...', all the .dll files will be moved into "Excluded Files" folders at the bottom of the folder diff display. They will be out of your way, but can still view and manipulate them if you really need to.
You can also do it another way, which will reduce your "Excluded Files" folder to just one, but you won't be able to manipulate any of the files it contains because the path will be corrupt (but if you just want them out of your way, it doesn't matter).
```
-//depot/foo.../*.dll //CLIENT/foo.../*.dll
```