What are reserved filenames for various platforms?

Question

I\'m not asking about general syntactic rules for file names. I mean gotchas that jump out of nowhere and bite you. For example, trying to name a file \"COM\" on Wi

Answer 1

As others have said, device names like COM1 are not possible as filenames under Windows because they are reserved devices.

However, there is an escape method to create and access files with these reserved names, for example, this command will redirect the output of the ver command into a file called COM1:

ver > "\\?\C:\Users\username\COM1"

Now you will have a file called COM1 that 99% of programs won't be able to open, and will probably freeze if you try to access.

Here's the Microsoft article that explains how this "file namespace" works. Basically it tells Windows not to do any string processing on the text and to pass it straight through to the filesystem. This trick can also be used to work with paths longer than 260 characters.