The sigpending
function returns the set of signals that are blocked
from delivery and currently pending for the calling process.
就是说，返回的信号，是被已经产生，但因为被block而没有deliver的。
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <errno.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <errno.h>
#include <unistd.h>
static void sig_quit(int);
int
main(void)
{
sigset_t newmask, oldmask, pendmask;
if (signal(SIGQUIT, sig_quit) == SIG_ERR)
perror("can't catch SIGQUIT");
/*
* Block SIGQUIT and save current signal mask.
*/
sigemptyset(&newmask);
sigaddset(&newmask, SIGQUIT);
if (sigprocmask(SIG_BLOCK, &newmask, &oldmask) < 0)
perror("SIG_BLOCK error");
sleep(5); /* SIGQUIT here will remain pending */
if (sigpending(&pendmask) < 0)
perror("sigpending error");
if (sigismember(&pendmask, SIGQUIT))
printf("/nSIGQUIT pending/n");
/*
* Reset signal mask which unblocks SIGQUIT.
*/
if (sigprocmask(SIG_SETMASK, &oldmask, NULL) < 0)
perror("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)
perror("can't reset SIGQUIT");
}