Question: Every time I use a firebase command this error occurs:

```
...\WEBRTCTest\FirebaseRTC> firebase use --add

Error: Invalid project id: \.

```

```
\WEBRTCTest\FirebaseRTC> firebase use --clear

Error: Invalid project id: \.

```

The error occured after I accidently run the command:

```
firebase use \

```

Prior to that all was working fine.

I tried to reinstall firebase-tools using npm and also re-cloning the example project from github.
Also tried to logout using `firebase logout` but it gives me the same error:

```
\WEBRTCTest\FirebaseRTC> firebase use --clear

Error: Invalid project id: \.

```

I´m thankful for any idea as i´m stuck right now.

Answer: 
Not sure why it works now. But I found a work-around: It´s working again after cloning the project in a new folder.
The Firebase CLI keeps information about the current project in a (hidden) file called `.firebaserc`. It looks like your `.firebaserc` file got corrupted, so you might want to delete the file and then run `firebase use` or `firebase add` again .