1.程序

#include "apue.h"
#include <setjmp.h>
#include <time.h>

static sigjmp_buf jmpbuf;
static volatile sig_atomic_t canjump;
void pr_mask(const char *str)
{
sigset_t sigset;
int errno_save;

errno_save = errno;
if (sigprocmask(0, NULL, &sigset) < 0)
err_sys("sigprocmask error");

printf("%s", str);

if (sigismember(&sigset, SIGINT)) printf("SIGINT");
if (sigismember(&sigset, SIGQUIT)) printf("SIGQUIT");
if (sigismember(&sigset, SIGUSR1)) printf("SIGUSR1");
if (sigismember(&sigset, SIGALRM)) printf("SIGALRM");

printf("\n");

errno = errno_save;
}

static void sig_usr1(int signo)
{
time_t starttime;
if (canjump == 0)
return ;

pr_mask("starting sig_usr1:");
alarm(3);
starttime = time(NULL);
for (;;)
if (time(NULL) > starttime + 5)
break;
pr_mask("finishing sig_usr1:");
canjump = 0;
siglongjmp(jmpbuf, 1);
}

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

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: ");

if (sigsetjmp(jmpbuf, 1))
{
pr_mask("ending main: ");
exit(0);
}
canjump = 1;
for (;;)
pause();
}

2.结果

xiaoheng@ubuntuxh:~/Program/apue/apue10/1010$ ./1015 &
[1] 18966
xiaoheng@ubuntuxh:~/Program/apue/apue10/1010$ starting main:
kill -USR1 18966
starting sig_usr1:
xiaoheng@ubuntuxh:~/Program/apue/apue10/1010$ int sig_alrm:
finishing sig_usr1:
ending main:

没有打印SIGUSR1跟SIGALRM