To do this absolutely properly, you neet to write a virtual filesystem. And I imagine that's quite difficult to do in perl.

By "absolutely properly", I mean handling all possible operations on the file.

The next best thing may be to move the samba share to a Linux server, and use the pipes, but my gut tells me there's race conditions, timeouts, etc., which would mean that in some scenarios, bossman may overwrite files.

Actually, I take some of that back - what you really want is to pull it off the share, and make it accessable only to multi-user-editing software. Period. And tell bossman that due to the problems you've had with the file, you've found a solution that will keep all changes safe.

To be honest, it's probably easier to quit and find a new job ;->. But that's no guarantee you'll get a brighter PHB...

Nah, write an syscall wrapper around open and apply it to the samba process.

Of just hack the samba source?

Better a sysopen wrapper.

Suppose you had a continuous process (or a frequent cron job) on the samba server that checked the file's modification time -- e.g. at intervals of 5 sec or less. As soon as the process detects that the file has been modified relative to the previous check, the current version of the file is copied to someplace safe with a distinctive appendage to the file name based on the current system time.

This will drastically reduce the likelihood that the person who saves a new version after a 3-hour (or 3-day) editing session will obliterate other people's changes that were saved during the interim. The probability of two people issuing save commands within the same short interval, though not nil, is perhaps comfortably low. (At least, it'll be a big improvement over the status quo.)

There's still the problem of detecting when two or more successive saves contain divergent changes relative to some earlier version, and then reconciling them. For this, it might suffice if the short-interval "check-for-update" process runs a backtick "diff3" command each time the file is modified, comparing the newest version just detected with the previous two. (I haven't used diff3, but it is a standard GNU utility, and I think it would do nicely for this job.)

(Yes, I know I'm a year late here.) If you can convince them to use some other editor instead of notepad (better try with some editor with very similar appearience and feel) you may be able to write a macro hook in it to check for the file being notified. You might not even have to do any programming, as some editors already check when saving if the modification date of the file is later then when it was opened, and warn the user about it. That of course might still fail if they save almost in the same moment, but you can get over that if the editor also locks the file at saving automatically (which is also not an unknown editor feature).

This also works partially if you can convince only some of the people, as it would still warn him if he saves the file when someone else have changed it since he's loaded it.

(Update: note that I've also updated my reply to the parent thread.)