10.13 sigpending函数

Posted 2020-07-10 U201013687

函数sigpending被阻塞发送并且当前被调用该函数的进程挂起的信号，这个信号集通过参数set返回.

#include <signal.h>
int sigpending(sigset_t *set);
    Returns:0 if OK,-1 on error.

Example

#include "apue.h"
static void sig_quit(int);
int main(void)
{
        sigset_t        newmask,oldmask,pendmask;
        if(signal(SIGQUIT, sig_quit) == SIG_ERR)
                err_sys("can‘t catch SIGQUIT");
        /*
         * Block SIGQUIT and save current signal mask
         *
         */
        sigemptyset(&newmask);
        sigaddset(&newmask, SIGQUIT);
        if(sigprocmask(SIG_BLOCK, &newmask, &oldmask) < 0)
                err_sys("SIG_BLOCK error");
        sleep(5);       /*SIGOUT here will remain pending*/
        if(sigpending(&pendmask) < 0)
                err_sys("sigpending error");
        if(sigismember(&pendmask, SIGQUIT))
                printf("\nSIGQUIT pending\n");
        /*
         * Restore signal mask whick unblocks SIGQUIT.
         */
        if(sigprocmask(SIG_SETMASK, &oldmask, NULL) < 0)
                err_sys("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)
                err_sys("can‘t reset SIGQUIT");
}

执行效果如下图:

[email protected]:~/UnixProgram/Chapter10$ ./10_15.exe
^\^\^\
SIGQUIT pending
caught SIGQUIT
SIGQUIT unblocked
^\Quit
[email protected]:~/UnixProgram/Chapter10$ ./10_15.exe
SIGQUIT unblocked
[email protected]:~/UnixProgram/Chapter10$ 

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