I also gdb'' d the code, and at this part of the code, it gives such an error: Program received signal SIGSEGV, Segmentation fault. 0x00000083 in ?? () If you could help me, I would appreciate. ****************************************************************************** Hi, I have a small question about tc''s source code. I m trying to compile the code by itself, and for this purpose i ve created a big .c file that includes all the sources it uses. the reason behind this to make a small modification for my school project. But whenever I try to do "tc qdisc add ..." or "tc class add..", it gives the error segmentation fault, and it gives this error in this code section of tc_qdisc_modify function: if (q->parse_qopt(q, argc, argv, &req.n)) I could not find why this error has occured for 3 days. I would appreciate, if you could help me or suggest something.