How Do I Launch `Spark-Shell` from the Command Line?

The following commands should work:

cd /home/m1/workspace/spark-1.6.1/bin
./spark-shell

I see that you have other copies of spark-shell here:

/home/m1/workspace/spark-2.0.0-bin-hadoop2.6/bin/spark-shell
/home/m1/Téléchargements/spark-1.6.1/bin/spark-shell
/home/m1/Téléchargements/spark-1.6.1-bin-hadoop2.6/bin/spark‌​-shell
/home/m1/Téléchargements/spark-2.0.0-bin-hadoop2.6/bin/spark‌​-shell

and these can be opened using the same pattern I have given in the first example or even entered into your $PATH for easier access...