Windows 10: What are the rules regarding casing of values for environment variable USERNAME in Windows?

One of my customers says that in his AD usernames have mixed case sometimes and besides that, that people are able to successfully login using another casing of usernames. So there might be an "ExampleUser" in the AD and Windows allows them to login with "exampleUSER" etc. as well.

But what is the impact on the environment variable "USERNAME"?

I have tested a bit myself without an AD and in all of my tests "USERNAME" had the value of the username as it has been created. So in case of "ExampleUser" created in Windows, using the login "EXAMPLEuser" provided "ExampleUser" as "USERNAME". That happened for RDP where users are free to input usernames as well as using "runas".

My customer said that this is not the case for him at least sometimes, but instead if "ExampleUser" in the AD logs in using "exampleUSER", "USERNAME" really contains the value of the current login, "exampleUSER". I've found another question describing that as well:

> For some users in this office, %USERNAME% is always in the case they type it when logging in.

> For other users, %USERNAME has until recently always been in the canonical case (for a user logging in as elenasimpson it returns ElenaSimpson), but last week mysteriously started only doing this sometimes and the rest of the time returning it as typed. Rebooting often toggles to the other behaviour.

What I did not found is any official docs from MS of what is the value of "USERNAME" under which setups and inputs of users. Are there any rules one can rely on?

Thanks!

:)

 

System environment variable won't stick


Running Win10 Home on an Acer Spin 3, 64bit, i7cpu. I try to add a path to the system environment variables by:

1. Control Panel > System > Advanced system settings > Advanced tab > Environment variables

2. The "Environment Variables" window opens.
3. In the "System Variables" pane I select "Path" and click the EDIT button.
4. A list of the current system paths is displayed.
5. I click the NEW button, browse to the path I want to add which is "C:\Python36-32" and click OK. The path "C:\Python36-32" is added to the list of current system paths.
6. I click OK and am returned to the "Environment Variables" window.
7. I click the "X" at the top right to close the "Environment Variables" window.

Now if I click the "Environment Variables" button again (end of step-1) and repeat steps 2-4, the new path I added in step-5 is gone. IOW, adding a new path won't stick.

What am I doing wrong?

 

Searching environment variable in list

I'm using a command that gives me a list of environment variables. When searching in the list, I want to find all environment variables with the word
EXTERNAL; using the following command all that is occurring is all the environment variables are being listed instead of those environment variables with the word
EXTERNAL ?

findstr /c "EXTERNAL"

 

System environment variable won't stick

Yes, there's an OK button for each step.