The Challenge

Let's get down to business. You hate me, /prog/, and I hate you. Being a Calculus, I am unsatisfied with my programming skill and seek improvement. I challenge any of you who take pride in your skill with C to engage in the following game:

- Put down a challenge. A criteria for a program that both of us shall implement with C.
- Wait for me to accept your challenge. I don't accept those stupid challenges you find on that project euler website. Math doesn't interest me, "such that there exists"-boys. The exercises in K&R2 and, perhaps simple Unix programs, are good examples of the kinds of programs that interest me. You know, useful ones.
- Post your code.
- Wait for me to post my code.

If your program is fancier than my own and yields little criticism from one Lambda A. Calculus, I shall leave /prog/. I'm open to other stakes as well.

I await your challenges and, if any stupid stack boys want to challenge me, go for it.

The nicest implementation of cat(1):

#include "unistd.h"
int O=!(0xbeef
       -0xf00d
       -0xbaad
       +0xdead
       +0xd1e)
       <<020,*_O,( *_[002]
       )(
int,
       void*,int)={write,
       read}; int __(){int O_=1,_0 = O_[_]
       (        
        ++O_,
         _O,
          O
       );
      (O_^=O_)[_]
      (
        ++O_,
         _O,
         _0
      );
      return _0;}
      
      main(){
        for(_O = malloc(O);
        __(););
      }