The Emscripten Command Prompt is used to call Emscripten tools from the command line on Windows.
The prompt can be launched from the file system by locating and opening the file emcmdprompt.bat.
The Emscripten Command Prompt is configured with the correct system paths and settings to point to the active Emscripten tools. From within the prompt you can call emsdk to change the current SDK or tools.
The tool is not intended to be run from an existing command line prompt.
However, if emcmdprompt.bat is called on the command line, a nested Emscripten command prompt is spawned within the current prompt (note that this is not necessarily obvious). You can then use this prompt to access the SDK tools. To exit the nested command prompt, type exit and then press the Enter key.