MS Teams channels cannot contain MS-DOS device names

One time I thought it would be funny to run a shell script that looped through every Windows share on the network and tried to open `CON/CON` on it, resulting in a prompt Blue Screen of Death for each machine.

For some reason my friends did not think it was funny.

But maybe it's more about what everyone else might do with a channel name. Ie they might cut & paste it anywhere, and I guess windows users aren't expected to escape their own strings when pasted into cmd or powershell or wsl.

The teams code itself can probably handle it just fine, but maybe not all the unknown janky random things out there that might handle channel names.

Other people have pointed out the SharePoint folders associated with the channels. Not sure I would excuse that myself since it's easy enough to just escape or modify or encode to create a safe version for the directory, but maybe it's important elsewhere for the channel name and the directory name to be identical. Within one app you could simply encode and decode both the channel name and directory name the same way and totally hide the encoding from the user, but if the directory is used outside of the app, then it would look bad with URL encoding or something that everything else will just display as it is, not decoded.

So the directory has to be safe for everything else, and so the channel name has to be the same.

Essentially choosing to have these limits rather than have directory names that look ugly sometimes. It's ultimately not even a safety or breakage thing, just a cosmetic thing. All directories will always look natural and good, because they don't allow anything that would have needed to be encoded.

Have to respect MS' backwards compatibility fanaticism. Impossibly as if a native port of MS Teams would be created for MS-DOS 3.1 (hahahaha). When more plausibly the MS Teams servers run on an ancient crazy proprietary MS-DOS 3.1 mainframe (still implausible, but hey).

I know that this device name restriction also applies to Windows file names, so it's not that surprising (if you are inclined to be less fun than possible), but if you like fun, you can pretend the former.

Relevant frag link: https://learn.microsoft.com/en-us/microsoftteams/limits-spec...

  if(version.StartsWith(“Windows 9”)) {
    /* 95 and 98 */
    ...
  }

> forms, CON, CONIN$, CONOUT$, PRN, AUX, NUL, COM1 to COM9, LPT1 to LPT9, desktop.ini, _vti_

If they have to restrict those because some user input is going straight into their FS, then they mucked up. Probably should have been given a safe ID (perhaps uuid4, perhaps something more like a digest of the channel name instead of using the user input directly.

For me it's a smell when someone says "You cannot use these characters". I automatically think "Why not? You're not using this unencoded or plaintext, right?" eg passwords, or usernames, or content that will show up on a webpage like a comment or such.

This all being said, perhaps it's just an easter egg gone sideways... Perhaps they were just trying to have a bit of fun :)

    "rm -rf /*"

Surely that is something to aim for because nothing shall ever go wrong?

Thankfully having a file named https://example.org is illegal in Linux (and Windows too right?).

Seriously: is this a problem of you? And if it's a problem, where do you draw the line?

What about codepoint 0? What about Hangul fillers and RLO characters: do you think applications who refuse these do suck?

There are, thankfully, limitation on what filenames can contain. And I think the restrictions aren't anywhere near restrictive enough. Same for usernames, same for channels, same for oh-so-many things.

Does anyone really find it problematic that, say, Twitter only allows visible alphanumeric characters and underscore? (and 15 chars max)

This seems very smart to me. I take that any day over longing for people being able to use poop emojis in their usernames and channels names.

So my company can only have 25 “general” teams.

I think it would be neat to learn the rationale behind some of these settings.

But 'forms'? Why is 'forms' a bad word?

(1) http://astrodigital.org/space/stshorse.html

AFAIK those still can’t be used as file system names, so I’m assuming it’s related to that.

Tim Paterson’s Revenge.

Having to escape everything or replace names with stable guids is not a good relpacement for storing \whatever\logs\channelname or whatever the need may be. Especially for systems that are hard bound to windows filesystems or Sharepoint to begin with.

I bet there are apps on other OS:es where you CAN name things a "\0" sequence or "/" and for each such app I imagine there are people who regret making that possible.

Maybe alongside the school of computer science at universities we’ll have a school of computer archeology and a school of computer ethics where we’ll be taught not to use negative reinforcement for AI training…

  "some horrible $MS product I don't use does some horrible $MS-like thing"

Still incredibly sad, but not as insane as if you couldn't use the names inside a chat.

c:\> copy CON: COMMAND.COM <furious streaming begins>