text: // PROGRAMA p01a.c
  #include <stdio.h>
  #include <signal.h>
  #include <unistd.h>
  #include <stdlib.h>
  
  void sigint_handler(int signo)
  {
      printf("In SIGINT handler ...\n");
  }
  
  int main(void)
  {
      if (signal(SIGINT, sigint_handler) < 0)
      {
          fprintf(stderr, "Unable to install SIGINT handler\n");
          exit(1);
      }
      printf("Sleeping for 30 seconds ...\n");
      
      int r = sleep(30);
      while(r > 0){
          r = sleep(r);
      }
  
      printf("Waking up ...\n");
      exit(0);
  }