signal.c

   1 /*
   2  * An example of signal usage
   3  */
   4
   5 #include <stdio.h>
   6 #include <signal.h>
   7 #include <stdlib.h>
   8
   9 volatile sig_atomic_t quitflag; /* set by the handler */
  10
  11 static void sig_int(int signo)
  12 {
  13         if (signo == SIGINT)
  14                 printf("interrupt\n");
  15         else if (signo == SIGQUIT)
  16                 quitflag = 1;
  17 }
  18
  19 int main(void)
  20 {
  21         sigset_t newmask, oldmask, zeromask;
  22
  23         if (signal(SIGINT, sig_int) == SIG_ERR) {
  24                 perror("signal(SIGINT)");
  25                 exit(1);
  26         }
  27
  28         if (signal(SIGQUIT, sig_int) == SIG_ERR) {
  29                 perror("signal(SIGQUIT)");
  30                 exit(1);
  31         }
  32
  33         sigemptyset(&zeromask);
  34         sigemptyset(&newmask);
  35         sigaddset(&newmask, SIGQUIT);
  36
  37         /*
  38          * Block SIGQUIT and save current signal mask
  39          */
  40         if (sigprocmask(SIG_BLOCK, &newmask, &oldmask) < 0) {
  41                 perror("sigprocmask()");
  42                 exit(1);
  43         }
  44
  45         while (!quitflag)
  46                 sigsuspend(&zeromask);
  47
  48         /*
  49          * SIGQUIT has been caught and is now blocked; do whatever
  50          */
  51         printf("SIGQUIT caught!\n");
  52
  53         /*
  54          * Reset signal mask which unblocks SIGQUIT
  55          */
  56         if (sigprocmask(SIG_SETMASK, &oldmask, NULL) < 0) {
  57                 perror("sigprocmask()");
  58                 exit(1);
  59         }
  60
  61         return 0;
  62 }
  63