Command line to remove an environment variable from the OS level configuration

Question

Windows has the setx command:

Description:
    Creates or modifies environment variables in the user or system
    environment.

So you can

Answer 1

To remove the variable from the current command session without removing it permanently, use the regular built-in set command - just put nothing after the equals sign:

set FOOBAR=

To confirm, run set with no arguments and check the current environment. The variable should be missing from the list entirely.

Note: this will only remove the variable from the current environment - it will not persist the change to the registry. When a new command process is started, the variable will be back.