opening frontend failed: No such file or directory

femon: invalid option -- '-' usage: femon [options] -H : human readable output -A : Acoustical mode. A sound indicates the signal quality. -r : If 'Acoustical mode' is active it tells the application is called remotely via ssh. The sound is heard on the 'real' machine but. The user has to be root. -a number : use given adapter (default 0) -f number : use given frontend (default 0) -c number : samples to take (default 0 = infinite)