dcheck, icheck, and clri were in 6th Edition. You can read about them in the Fielder and Hunter book on AT&T Unix System 5 Release 4, which describes them as "

dcheck, icheck, and clri were in 6th Edition. You can read about them in the Fielder and Hunter book on AT&T Unix System 5 Release 4, which describes them as "antiques" that one should only use if one's Unix has no fsck. (-: