root/mmap/memmap.c

DEFINITIONS

1. main

#include<stdio.h>
#include<sys/fcntl.h>
#include<sys/mman.h>

struct data {
        int x, y;
        double xstat, ystat;
};


int main() {
        int fd,i;
        struct data *arr;
        double sumx,sumy;

        fd=open("data.bin",O_RDWR);

        arr=(struct data *)mmap(0, 1000*sizeof(struct data), 
                PROT_READ|PROT_WRITE,
                MAP_SHARED, fd, 0);

        sumx=sumy=0;
        for (i=0;i<1000;i++) {
                sumx += arr[i].x;
                sumy += arr[i].y;
        }
        for (i=0;i<1000;i++) {
                arr[i].xstat = arr[i].x/sumx;
                arr[i].ystat = arr[i].y/sumy;
        }
        munmap(arr,1000);
        close(fd);
        return 0;
}