#include <iostream>

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <pwd.h>

#define GRABBERLOCK "/tmp/grabberlock"	/* file used as the lock flag	*/

int lock(char *f);
void unlock(char *f);

int lock(char *f)
{
	int fd;
	struct stat statbuf;	/* structure used to hold file info	*/

	if((fd = open(f,O_WRONLY | O_CREAT | O_EXCL, 0644)) == -1)

	/* permission 0644 on lock gives you/group/world of -rw-r--r 	*/
	{
		printf("\nSorry, %s is already locked by ", f);
		stat(f, &statbuf);
		printf("%s\n", getpwuid(statbuf.st_uid)->pw_name);
		return -1;
	}
	else
	{
	 	close(fd);
	 	return 0;
	}
}

void unlock(char *f)
{	/* invokes a system call which removes the file (effectively just
 removes the link to the file in the directory table). */
	unlink(f);
}

int main (int argc, char * const argv[])
	{
		if(lock(GRABBERLOCK) == -1)
		{
			exit(EXIT_FAILURE);
		}
		else
		{
			printf("\nUsing Resouce for 5 Seconds ... \n");
			sleep(5);
			printf("\nDone Using Resource.\n");
			unlock(GRABBERLOCK);
			exit(EXIT_SUCCESS);
		}
		return 0;
	};