critical.c

unix高级编程源代码.<<unix高级编程>>

#include	<signal.h>
#include	"ourhdr.h"

static void	sig_quit(int);

int
main(void)
{
	sigset_t	newmask, oldmask, pendmask;

	if (signal(SIGQUIT, sig_quit) == SIG_ERR)
		err_sys("can't catch SIGQUIT");

	sigemptyset(&newmask);
	sigaddset(&newmask, SIGQUIT);
					/* block SIGQUIT and save current signal mask */
	if (sigprocmask(SIG_BLOCK, &newmask, &oldmask) < 0)
		err_sys("SIG_BLOCK error");

	sleep(5);		/* SIGQUIT here will remain pending */

	if (sigpending(&pendmask) < 0)
		err_sys("sigpending error");
	if (sigismember(&pendmask, SIGQUIT))
		printf("\nSIGQUIT pending\n");

					/* reset signal mask which unblocks SIGQUIT */
	if (sigprocmask(SIG_SETMASK, &oldmask, NULL) < 0)
		err_sys("SIG_SETMASK error");
	printf("SIGQUIT unblocked\n");

	sleep(5);		/* SIGQUIT here will terminate with core file */

	exit(0);
}

static void
sig_quit(int signo)
{
	printf("caught SIGQUIT\n");

	if (signal(SIGQUIT, SIG_DFL) == SIG_ERR)
		err_sys("can't reset SIGQUIT");
	return;
}