mask.c

unix高级编程源代码.<<unix高级编程>>

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

static void						sig_usr1(int), sig_alrm(int);
static sigjmp_buf				jmpbuf;
static volatile sig_atomic_t	canjump;

int
main(void)
{
	if (signal(SIGUSR1, sig_usr1) == SIG_ERR)
		err_sys("signal(SIGUSR1) error");
	if (signal(SIGALRM, sig_alrm) == SIG_ERR)
		err_sys("signal(SIGALRM) error");
	pr_mask("starting main: ");		/* {Prog prmask} */

	if (sigsetjmp(jmpbuf, 1)) {
		pr_mask("ending main: ");
		exit(0);
	}
	canjump = 1;	/* now sigsetjmp() is OK */

	for ( ; ; )
		pause();
}
static void
sig_usr1(int signo)
{
	time_t	starttime;

	if (canjump == 0)
		return;		/* unexpected signal, ignore */

	pr_mask("starting sig_usr1: ");

	alarm(3);				/* SIGALRM in 3 seconds */

	starttime = time(NULL);
	for ( ; ; )				/* busy wait for 5 seconds */
		if (time(NULL) > starttime + 5)
			break;

	pr_mask("finishing sig_usr1: ");

	canjump = 0;
	siglongjmp(jmpbuf, 1);	/* jump back to main, don't return */
}

static void
sig_alrm(int signo)
{
	pr_mask("in sig_alrm: ");
	return;
}