Editing Prefs (Options)

[Budge]

I have been using a version of ffmpeg which I downloaded when I had 
problems more than a year ago.  I assume that the distribution repo site 
version will by now meet the requirements so wish to take out the ffmpeg 
path line in my options file.

Rather than edit the file I thought I would use --prefs-del.  Is that 
the correct approach and what is syntax to specify the relevant line.  I 
tried using the line as in the file but nothing happened.  Should it be 
in quotes or what?