sigpending显示当前进程有哪个信号被pending

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");
}