5 #include"apue.h"
  6 static void sig_quit(int);
  7 
  8 int main(void)
  9 {
 10     sigset_t newmask,oldmask,pendmask;
 11 
 12     if(signal(SIGQUIT,sig_quit) == SIG_ERR)
 13         err_sys("can't catch SIGQUIT");
 14 
 15     sigemptyset(&newmask);
 16     sigaddset(&newmask,SIGQUIT);
 17 
 18     if(sigprocmask(SIG_BLOCK, &newmask, &oldmask) < 0)
 19         err_sys("SIG_BLOCK error");
 20 
 21     sleep(5);
 22 
 23     if(sigpending(&pendmask) < 0)
 24         err_sys("sigpending error");
 25     if(sigismember(&pendmask, SIGQUIT))
 26         printf("\nSIGQUIT pending\n");
 27 
 28     if(sigprocmask(SIG_SETMASK, &oldmask, NULL) <0)
 29         err_sys("SIG_SETMASK error");
 30     printf("SIGQUIT unblocked\n");
 31     sleep(5);
 32     exit(0);
 33 }
 34 static void sig_quit(int signo)
 35 {
 36     printf("caught SIGQUIT\n");
 37     if(signal(SIGQUIT, SIG_DFL) == SIG_ERR)
 38         err_sys("can't reset SIGQUIT");
 39 }
~