Command prompt does not stop when trying to launch ipython notebook

The comments seem to have been resolved, so I will edit and transfer the answers.

Solution with Command Line Options

If the logging level is set to DEBUG, try adding --log-level=CRITICAL to the optional switch at the command line.

>ipython --log-level=CRITICAL

Resolution by Configuration Change

You must enter --log-level=CRITICAL every time (on the optional switch on the command line) to start successfully.
Can't I save my settings somewhere?

Try running ipython notebook --generate-config first.
After executing it, I think a file called ~/.jupyter/jupyter_notebook_config.py has been created.
Add c.Application.log_level=50 to this jupyter_notebook_config.py.