why do I get an Error when I set ROS_WORKSPACE ?

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Hi, I have installed Ros_groovy. And I am creating my workspace with the tutorial: "Installing and Configuring Your ROS Environment"

and everything goes okay, until I write:

john@john-G41D3C:~$ rosws set ~/groovy_workspace/sandbox

ERROR in config: Command requires a target workspace.

I try even with other name of my workspace, but i get the same error:

john@john-G41D3C:~$ rosws set ~/fuerte_workspace/sandbox

ERROR in config: Command requires a target workspace.

What am i doing wrong?