#!/bin/bash
#sample script to start a program, permit it to run for a predefined amount of CPU time, then kill it.
#
progID="gmplayer"
$progID &
mypid=`eval ps ax|grep "$progID"|grep -iv "grep"| awk '{print $1}'`
echo "mypid $mypid"
mins=0
killmins=5
while [ $mins -lt $killmins ]; do
  usePID=`eval ps ax|grep "$progID"|grep -iv "grep"| awk '{print $4}'`
  hours=`eval echo "$usePID" | awk -F\: '{print $1}'`
  mins=`eval echo "$usePID" | awk -F\: '{print $2}'`
  sleep 1
  echo "$usePID"
  echo "$hours"
  echo "$mins"
done
kill "$mypid"

#include <stddef.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <time.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/time.h>

#define SHELL "/bin/sh"

pid_t pid;
int status = 123;

void sigalrm_catch(int sig)
{
	fprintf(stderr, "lim: child process timeout: sending SIGKILL");
	kill(pid, SIGKILL);
	exit(-4);
}

void exec_limit(int max_time, char *cmd)
{
	struct itimerval tm;
	pid = fork();
	if (pid == 0){
		// child process: execute the shell command
		execl(SHELL, SHELL, "-c", cmd, NULL);
		fprintf(stderr, "lim: could not exec the shell\n");
		status = -3;
	} else if (pid < 0){
		// fork failed
		status = -3;
		fprintf(stderr, "lim: could not fork\n");
	} else {
		tm.it_interval.tv_sec = 0;
		tm.it_interval.tv_usec = 0;
		tm.it_value.tv_sec = max_time / 1000;
		tm.it_value.tv_usec = max_time % 1000;
		signal(SIGALRM, &sigalrm_catch);
		setitimer(ITIMER_REAL, &tm, NULL);
		waitpid(pid, &status, 0);
	}
}

int main(int argc, char **argv)
{
	int i, l, max_time, cmd_len;
	char *cmd, *p;

	if (argc <= 2){
		printf("executes a command and limits its execution time\n"
			"syntax: lim timeout command\n"
			"\ttimeout is specified in milliseconds\n\n"
		);
		return 0;
	}
	
	max_time = atoi(argv[1]);
	if (!max_time){
		fprintf(stderr, "lim: invalid timeout\n");
		return -1;
	}
	
	cmd_len = 0;
	for (i=2; i<argc; i++){
		cmd_len += strlen(argv[i]) + 1;
	}
	p = cmd = malloc(cmd_len);
	if (!cmd)
		return -2;
	for (i=2; i<argc; i++){
		l = strlen(argv[i]);
		memcpy(p, argv[i], l);
		p += l;
		*p++ = ' ';
	}
	*p = '\0';
	
	exec_limit(max_time, cmd);
	free(cmd);
	return status;
}