Quoting Eric Delcamp,

> Yes, I can use 'nslookup', but this cmd generate garbage (like DNS name and
> his IP-number). I want a command like :

> # cmd 194.51.118.33
> user33.alienor.fr

You can either use:

 1) nslookup -querytype=ptr 33.118.51.194.in-addr.arpa, and filter the output
 2) host 194.51.118.33, and filter the output (easier to do)
 3) write a tiny program yourself, using gethostbyaddr()

- Frank