/*
 * cpulimiter - run a program with a CPU time limit, printing a
 *              student-oriented message if the time limit is reached.
 * Someone must have written and circulated a program like this, but I can't
 * find it.
 * Alan J Rosenthal, 13 October 2000.
 * (Revised 2003, 2007 for the CSC 209/B09 web page.)
 */

#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <sys/signal.h>


void sigchld(int x)
{
    _exit(0);
}


int main(int argc, char **argv)
{
    int pid;

    if (argc < 2) {
	fprintf(stderr, "usage: limiter command\n");
	return(1);
    }
    if ((pid = fork()) == -1) {
	perror("fork");
	return(1);
    }
    if (pid) {
	signal(SIGCHLD, sigchld);
	sleep(10);
	/* won't get here if SIGCHLD happened */
	signal(SIGCHLD, SIG_DFL);
	if (kill(pid, 9) == 0 || errno != ESRCH /* No such process */)
	    fprintf(stderr, "Time limit exceeded.  Probably in an infinite loop.\n");
    } else {
	argv++;
	if (execv(argv[0], argv))
	    perror(argv[0]);
    }

    return(0);
}