Command:   diskcheck - check a disk for bad sectors
Syntax:    diskcheck device start count
Flags:     (none)
Examples:  diskcheck /dev/at0 0 1200 # Check 1.2 MB diskette
           diskcheck /dev/at0 100 50 # Check blocks 100 to 149

     Diskcheck checks a disk for bad sectors by reading in each  sector,
writing  a  known  bit pattern onto it, reading it back in and comparing
with what was written.  This check is then  done  a  second  time.   Bad
sectors  are reported.  After each sector is tested, the original sector
is restored.  Only use this program on unmounted partitions.  Killing it
part way through may result in lost data.