This is the english translation of the original german blog post that can be found here.
Anyone who wants to produce or process data in different character sets or location, must be able to adapt its client environment dynamically.
In the world of Oracle tools this behavior is controlled by the environment variable $NLS_LANG.
In contrast, the modern SQLcl does not evaluate $NLS_LANG. The tool is written in Java and automatically uses the settings of the session it was started from.