signal.c

   1 /*
   2  * Signal usage example
   3  *
   4  * Luiz Fernando N. Capitulino <lcapitulino@mandriva.com.br>
   5  */
   6
   7 #include <stdio.h>
   8 #include <signal.h>
   9 #include <stdlib.h>
  10
  11 volatile sig_atomic_t quitflag; /* set by the handler */
  12
  13 static void sig_int(int signo)
  14 {
  15         if (signo == SIGINT)
  16                 printf("interrupt\n");
  17         else if (signo == SIGQUIT)
  18                 quitflag = 1;
  19 }
  20
  21 int main(void)
  22 {
  23         sigset_t newmask, oldmask, zeromask;
  24
  25         if (signal(SIGINT, sig_int) == SIG_ERR) {
  26                 perror("signal(SIGINT)");
  27                 exit(1);
  28         }
  29
  30         if (signal(SIGQUIT, sig_int) == SIG_ERR) {
  31                 perror("signal(SIGQUIT)");
  32                 exit(1);
  33         }
  34
  35         sigemptyset(&zeromask);
  36         sigemptyset(&newmask);
  37         sigaddset(&newmask, SIGQUIT);
  38
  39         /*
  40          * Block SIGQUIT and save current signal mask
  41          */
  42         if (sigprocmask(SIG_BLOCK, &newmask, &oldmask) < 0) {
  43                 perror("sigprocmask()");
  44                 exit(1);
  45         }
  46
  47         while (!quitflag)
  48                 sigsuspend(&zeromask);
  49
  50         /*
  51          * SIGQUIT has been caught and is now blocked; do whatever
  52          */
  53         printf("SIGQUIT caught!\n");
  54
  55         /*
  56          * Reset signal mask which unblocks SIGQUIT
  57          */
  58         if (sigprocmask(SIG_SETMASK, &oldmask, NULL) < 0) {
  59                 perror("sigprocmask()");
  60                 exit(1);
  61         }
  62
  63         return 0;
  64 }
  65