#define _GNU_SOURCE
#include <stdio.h>
#include <fcntl.h>
#include <string.h>
#include <stdlib.h>
#include <sys/time.h>
#define BLOCK_SIZE 1024
void main()
{
	char fname[10]="file_";
	char buffer[BLOCK_SIZE] __attribute__ ((__aligned__ (512)));
	struct timeval start, end;
	int fd=0;
	char *file;
	int i = 0;
	unsigned long long time;
	int status;
	char *names[] = {"1", "2", "3", "4", "5", "6", "7"};
	while (i < 7) {
		int pid = fork();
		if (pid == 0) {
			file = strcat(fname, names[i]);
			fd = open(fname, O_RDONLY | O_DIRECT);
			if (!fd) {
				printf("unable to open\n");
				exit(0);
			}
			printf("accessing %n", file);
			sleep(2);
			gettimeofday(&start, NULL);
			while(read(fd, buffer, BLOCK_SIZE));
			gettimeofday(&end, NULL);
			lseek(fd, 0, SEEK_SET);
			time = (end.tv_sec*1e6+end.tv_usec) - (start.tv_sec*1e6+start.tv_usec);
			//	printf("timestamp %llu - %llu\n", end.tv_sec*1e6+end.tv_usec, start.tv_sec*1e6+start.tv_usec);
			printf("time taken to read file # %d - %llu\n", i, time);
			sync();
			status = system("sudo /sbin/sysctl vm.drop_caches=3");
			sync();
			exit(0);
		}
		i++;
	}
	sleep(10);
	wait(&status);
}