sigpending

杰出天下 2011-04-15

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The sigpending function returns the set of signals that are blocked from delivery and currently pending for the calling process.

就是說，返回的信號，是被已經(jīng)產(chǎn)生，但因為被block而沒有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");
}