#include <sys/types.h>
#include <signal.h>
#include <unistd.h>
#include <stdio.h>

void myusr1(int sig, siginfo_t * theinfo, void * foo);

pid_t mypid;

main () {
   sigset_t  myset;

   /*  initialsize with sigemptyset(*set) or sigfillset(*set) */
   /*  examine with sigismember (*set, sig) */
   /*  change with sigdelset(*set, sig) or sigaddset(*set, sig) */

   struct sigaction myaction;

   /* sigacton has atleast
	sa_handler   pointer to function, SIG_DFL or SIG_IGN
	sa_sigaction
	sa_mask      a signal mask;
	sa_flags     see man page or book 
   */

   mypid = getpid();

   /*   sigemptyset(&myset);

   sigaddset(&myset, SIGUSR1);
   */
   sigemptyset(&myaction.sa_mask);
   myaction.sa_sigaction = myusr1;
   myaction.sa_flags = SA_SIGINFO;

   sigaction(SIGUSR1,  &myaction, NULL);

   sigemptyset(&myset);

   sigaddset(&myset, SIGUSR2);
   sigprocmask(SIG_BLOCK,&myset,NULL);

   sigemptyset(&myset);
   sigprocmask(SIG_BLOCK,NULL,&myset);
   if (1== sigismember(&myset,SIGUSR1)) {
      printf("The SIGUSR1 is blocked\n");
   }
   if (1== sigismember(&myset,SIGUSR2)) {
      printf("The SIGUSR2 is blocked\n");
   }

   printf("All set up in %d \n",mypid);
   while (1) {
     pause();
   }
}

void myusr1(int sig, siginfo_t * theinfo, void * foo) {

    sigset_t localset;

    printf("SIGUSR1 called\n");

    printf("Some more information:\n");
    printf(" pid = %d\n", theinfo->si_pid);
    printf(" uid = %d\n", theinfo->si_uid);
    printf(" signum = %d\n", theinfo->si_signo);

    sigpending( &localset); 

    if (1== sigismember(&localset,SIGUSR2)) {
       printf("There is a SIGUSR2 pending \n");
    }
    
}