simhash [ -s nshingles ] [ -f nfeatures ] [ file ]
       simhash [ -s nshingles ] [ -f nfeatures ] -w [ file ] ...
       simhash -c hashfile hashfile

This program is used to compute and compare similarity hashes of files.
       A similarity hash is a chunk of data that has the  property  that  some
       distance  metric  between files is proportional to some distance metric
       between the hashes.  Typically the similarity hash will be much smaller
       than the file itself.