+=item B<-c>, B<--checkgroups> I<filename template>
+
+Check each group against a list of valid newsgroups read from a file,
+one group on each line and ignoring everything after the first
+whitespace (so you can use a file in checkgroups format or (part of)
+your INN active file).
+
+The filename is taken from I<filename template>, amended by each B<--
+month> B<gatherstats> is processing, so that
+
+ gatherstats -m 2010-01:2010-12 -c checkgroups