critical.c

UNIX编程高级环境（第二版）的信号部分的程序源码

#include    <signal.h>
#include    "ourhdr.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");

    sigemptyset(&newmask);
    sigaddset(&newmask, SIGQUIT);
                    /* block SIGQUIT and save current signal mask */
    if (sigprocmask(SIG_BLOCK, &newmask, &oldmask) < 0)
        err_sys("SIG_BLOCK error");

    sleep(5);        /* SIGQUIT here will remain pending */

    if (sigpending(&pendmask) < 0)
        err_sys("sigpending error");
    if (sigismember(&pendmask, SIGQUIT))
        printf("\nSIGQUIT pending\n");

                    /* reset signal mask which 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");
    return;
}