20_1.c

#define _GNU_SOURCE
#include <signal.h>
#include "../tlpi-dist/signals/signal_functions.h" /* Declaration of printSigset() */
#include "tlpi_hdr.h"

static int sigCnt[NSIG]; /* Counts deliveries of each signal */
static volatile sig_atomic_t gotSigint = 0;
/* Set nonzero if SIGINT is delivered */

static void
handler(int sig)
{
    if (sig == SIGINT)
        gotSigint = 1;
    else
        sigCnt[sig]++;
}

int main(int argc, char *argv[])
{
    int n, numSecs;
    sigset_t pendingMask, blockingMask, emptyMask;
    struct sigaction act;

    sigemptyset(&act.sa_mask);
    act.sa_handler = handler;
    act.sa_flags = 0;

    printf("%s: PID is %ld\n", argv[0], (long)getpid());

    for (n = 1; n < NSIG; n++)
        sigaction(n, &act, NULL);

    if (argc > 1)
    {
        numSecs = getInt(argv[1], GN_GT_0, NULL);

        sigfillset(&blockingMask);
        if (sigprocmask(SIG_SETMASK, &blockingMask, NULL) == -1)
            errExit("sigprocmask");

        printf("%s: sleeping for %d seconds\n", argv[0], numSecs);
        sleep(numSecs);

        if (sigpending(&pendingMask) == -1)
            errExit("sigpending");

        printf("%s: pending signals are: \n", argv[0]);
        printSigset(stdout, "\t\t", &pendingMask);

        sigemptyset(&emptyMask); /* Unblock all signals */
        if (sigprocmask(SIG_SETMASK, &emptyMask, NULL) == -1)
            errExit("sigprocmask");
    }

    while (!gotSigint) /* Loop until SIGINT caught */
        continue;

    for (n = 1; n < NSIG; n++) /* Display number of signals received */
        if (sigCnt[n] != 0)
            printf("%s: signal %d caught %d time%s\n", argv[0], n,
                   sigCnt[n], (sigCnt[n] == 1) ? "" : "s");

    exit(EXIT_SUCCESS);
}