[ns] do not need core file

[Sencun Zhu <szhu1@ise.gmu.edu>]

Hi, Dear all:


     what can I do to prevent the executable file (like ns) from
generating core file,
since the core file generated is about 1Gb in my simulation when core dump 
, I doubt if the system uses a lot of memory in running time to record
memory map , thus it itself is also a reason for core dump.


thank you.


Sencun