/usr/bin/cluster: invalid option -- '-'
 option -- unrecognized
Usage: /usr/bin/cluster <options> graphfile
    -C k - generate no more than k clusters (0)
       0 : no limit
    -c k - use clustering method k (0)
       0 : use modularity
       1 : use modularity quality
    -o <outfile> - output file (stdout)
    -v   - verbose mode
    -?   - print usage