There is a race condition with this between the time a check is done vs the time the file is written.

It would be better if there is a session variable that could be set that would not allow overwrite of existing files.

Update: For example:

• PureFTPD's -r option forces a rename on upload of existing files.
• wu-ftpd is either by default or by a setting not able to overwrite files.

and my guess is that there are others. My only question is if any of them are user / client configurable. Now the question is, what does your ftp server support?