How to delete output file for rewriting?

edit

If you can give a very simple example that would be helpful. I'm not sure why your program wouldn't simply overwrite them, but I am not familiar with the wave library. It should certainly be possible in the notebook itself. But here is the generic answer for the Terminal, since that doesn't seem to be working:

First, a sample in the Terminal:

$ ls .sage/sage_notebook.sagenb/home/admin/215/cells/13/
sage0-size500-1046860989.jmol.zip   sage0-size500.jmol
$ rm ./sage/sage_notebook.sagenb/home/admin/215/cells/13/sage0-size500.jmol
$

Steps:

• Find the number of the worksheet you are looking at. This should be in the URL for the worksheet.
• Find the correct folder for the worksheet. That should be, normally, in a URL of the form above like .sage/sage_notebook.sagenb/home/admin/# but it could change based on the DOT_SAGE environment variable and whether you are the default user. Permissions could conceivably be an issue in that case.
• Look at the files in that worksheet's cells. See the example. You can see what cell the file lives in by using the "Edit" button, I think - there should be a tag there.
• Remove the file in question.