text: #ifndef ___POSIX_TIMER_EXAMPLE__4f2d423d_f4d4_4fdb_9b51_7223f3a3afc9__H___ 
  #define ___POSIX_TIMER_EXAMPLE__4f2d423d_f4d4_4fdb_9b51_7223f3a3afc9__H___
  
  #include <stdio.h>
  
  #include <pthread.h>
  #include <signal.h>
  #include <time.h>
  #include <unistd.h>
  #include <sys/types.h>
  
  // function prototypes 
  void before_main(void) __attribute__((constructor));
  void after_main(void) __attribute__((destructor));
  
  void start_clock(void);
  void clock_handler(int, siginfo_t* info, void*);
  
  #endif /* ___POSIX_TIMER_EXAMPLE__4f2d423d_f4d4_4fdb_9b51_7223f3a3afc9__H___ */