Thank you all! I've fixed the C program. Now I obtain the 7200 names *.uv.es for IP addresses 147.156.*.* in a few minutes and in a file which I can grep, sort, less, atp and lpr. -- Conrado Badenas (Assistant Lecturer) Department of Thermodynamics. University of Valencia c/. Doctor Moliner, 50 | e-m: Conrado.Badenas@uv.es 46100 Burjassot (Valencia) | Phn: +34-63864350 SPAIN | Fax: +34-63983385