+.TP
+\fB-e \fI<command>\fR, \fB--exec \fI<command>\fR
+execute the provided command for each group of identical files, with
+their names as arguments
+.TP
+\fB-f \fI<string>\fR, \fB--result-prefix \fI<string>\fR
+for each group of identical files, write one result file whose name is
+the given prefix string followed the group number, and containing one
+file name per line