signals/catch_rtsigs.c

#define _GNU_SOURCE
#include <string.h>
#include <signal.h>
#include "tlpi_hdr.h"

static volatile int handlerSleepTime;
static volatile int sigCnt = 0;         /* Number of signals received */
static volatile sig_atomic_t allDone = 0;

static void             /* Handler for signals established using SA_SIGINFO */
siginfoHandler(int sig, siginfo_t *si, void *ucontext)
{
    /* UNSAFE: This handler uses non-async-signal-safe functions
       (printf()); see Section 21.1.2) */

    /* SIGINT or SIGTERM can be used to terminate program */

    if (sig == SIGINT || sig == SIGTERM) {
        allDone = 1;
        return;
    }

    sigCnt++;
    printf("caught signal %d\n", sig);

    printf("    si_signo=%d, si_code=%d (%s), ", si->si_signo, si->si_code,
            (si->si_code == SI_USER) ? "SI_USER" :
            (si->si_code == SI_QUEUE) ? "SI_QUEUE" : "other");
    printf("si_value=%d\n", si->si_value.sival_int);
    printf("    si_pid=%ld, si_uid=%ld\n",
            (long) si->si_pid, (long) si->si_uid);

    sleep(handlerSleepTime);
}

int
main(int argc, char *argv[])
{
    struct sigaction sa;
    int sig;
    sigset_t prevMask, blockMask;

    if (argc > 1 && strcmp(argv[1], "--help") == 0)
        usageErr("%s [block-time [handler-sleep-time]]\n", argv[0]);

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

    handlerSleepTime = (argc > 2) ?
                getInt(argv[2], GN_NONNEG, "handler-sleep-time") : 1;

    /* Establish handler for most signals. During execution of the handler,
       mask all other signals to prevent handlers recursively interrupting
       each other (which would make the output hard to read). */

    sa.sa_sigaction = siginfoHandler;
    sa.sa_flags = SA_SIGINFO;
    sigfillset(&sa.sa_mask);

    for (sig = 1; sig < NSIG; sig++)
        if (sig != SIGTSTP && sig != SIGQUIT)
            sigaction(sig, &sa, NULL);

    /* Optionally block signals and sleep, allowing signals to be
       sent to us before they are unblocked and handled */

    if (argc > 1) {
        sigfillset(&blockMask);
        sigdelset(&blockMask, SIGINT);
        sigdelset(&blockMask, SIGTERM);

        if (sigprocmask(SIG_SETMASK, &blockMask, &prevMask) == -1)
            errExit("sigprocmask");

        printf("%s: signals blocked - sleeping %s seconds\n", argv[0], argv[1]);
        sleep(getInt(argv[1], GN_GT_0, "block-time"));
        printf("%s: sleep complete\n", argv[0]);

        if (sigprocmask(SIG_SETMASK, &prevMask, NULL) == -1)
            errExit("sigprocmask");
    }

    while (!allDone)                    /* Wait for incoming signals */
        pause();

    printf("Caught %d signals\n", sigCnt);
    exit(EXIT_SUCCESS);
}