That's my bad (I thought it looked weird when I typed it). Still the same syntax works with CON and any other reserved DOS devices
echo "hey DOS" > \\?\C:\temp\CON
del \\?\C:\temp\CON
While it can be "trivially" done, it's a hit or miss if any application actually supports it. You effectively need to deal with the NT path prefix \\?\ when dealing with the Win32 APIs to be able to open a handle to the file. The prefix essentially tells Win32 to back off and get the handle directly from the NT object manager.
echo "hey DOS" > \\?\C:\temp\CON
del \\?\C:\temp\CON
While it can be "trivially" done, it's a hit or miss if any application actually supports it. You effectively need to deal with the NT path prefix \\?\ when dealing with the Win32 APIs to be able to open a handle to the file. The prefix essentially tells Win32 to back off and get the handle directly from the NT object manager.