There are basically two rules to a well written C program (if I am now allowed to speak despite the public outcry).

1. Do not trust user input. This is a cardinal rule in whatever source. If the rule were followed vigorously in every case there would be 90% less exposure. When you take user input, filter. 2. Learn the standard and stick to it.

Finally #3 (unix) Write an application to do a certain thing well.