#include <stdio.h>

#include <stdlib.h>

#include <unistd.h>

#include <signal.h>

#include <sys/wait.h>

#include <sysexits.h>

#include <assert.h>

volatile sig_atomic_t caught_sig = 0;

static void signal_handler(int which)

{

    caught_sig = which;

}

static int wait_for_process(pid_t pid)

{

    int rv = EX_SOFTWARE;

    int status = 0;

    int i = 0;

    struct sigaction sig_handler;

    sig_handler.sa_handler = signal_handler;

    sig_handler.sa_flags = 0;

    sigaction(SIGALRM, &sig_handler, NULL);

    sigaction(SIGHUP, &sig_handler, NULL);

    sigaction(SIGINT, &sig_handler, NULL);

    sigaction(SIGUSR1, &sig_handler, NULL);

    sigaction(SIGTERM, &sig_handler, NULL);

    sigaction(SIGPIPE, &sig_handler, NULL);

    /* Loop forever waiting for the process to quit */

    for (i = 0; ;i++) {

        pid_t p = waitpid(pid, &status, 0);

        if (p == pid) {

            /* child exited.  Let's get out of here */

            rv = WIFEXITED(status) ?

                WEXITSTATUS(status) :

                (0x80 | WTERMSIG(status));

            break;

        } else {

            int sig = 0;

            switch (i) {

            case 0:

                /* On the first iteration, pass the signal through */

                sig = caught_sig > 0 ? caught_sig : SIGTERM;

                if (caught_sig == SIGALRM) {

                   fprintf(stderr, "Timeout.. killing the process\n");

                }

                break;

            case 1:

                sig = SIGTERM;

                break;

            default:

                sig = SIGKILL;

                break;

            }

            if (kill(pid, sig) < 0) {

                /* Kill failed.  Must have lost the process. :/ */

                perror("lost child when trying to kill");

            }

            /* Wait up to 5 seconds for the pid */

            alarm(5);

        }

    }

    return rv;

}

static int spawn_and_wait(char **argv)

{

    int rv = EX_SOFTWARE;

    pid_t pid = fork();

    switch (pid) {

    case -1:

        perror("fork");

        rv = EX_OSERR;

        break; /* NOTREACHED */

    case 0:

        execvp(argv[0], argv);

        perror("exec");

        rv = EX_SOFTWARE;

        break; /* NOTREACHED */

    default:

        rv = wait_for_process(pid);

    }

    return rv;

}

int main(int argc, char **argv)

{

    int naptime = 0;

    assert(argc > 2);

    naptime = atoi(argv[1]);

    assert(naptime > 0 && naptime < 1800);

    alarm(naptime);

    return spawn_and_wait(argv+2);

}