#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

typedef struct {
    char name[4];
    int age;
} people;

int main(int argc, char **argv)
{
    int fd, i;
    people *p_map;
    char temp;

    fd = open(argv[1], O_CREAT | O_RDWR | O_TRUNC, 0777);
    lseek(fd, sizeof(people) * 5 - 1, SEEK_SET);
    write(fd, "", 1);


    p_map = (people*)mmap(NULL, sizeof(people)*10, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);

    close(fd);

    temp = 'a';
    for (i = 0; i < 10; i++) {
        temp += 1;
        memcpy( ( *(p_map+i) ).name, &temp, 4);
        (*(p_map+i) ).name[1] = '\0';
        (*(p_map+i) ).age = 20+i;
    }

    printf("Initialize over \n");
    sleep(5);

    munmap(p_map, sizeof(people) * 10);
    printf("unmap OK \n");

    return 0;
}


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

typedef struct {
    char name[4];
    int age;
} people;

int main(int argc, char **argv)
{
    int fd, i;
    people *p_map;

    fd = open(argv[1], O_CREAT | O_RDWR, 0777);

    p_map = (people*)mmap(NULL, sizeof(people)*10, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);

    for (i = 0; i < 10; i++) {
        printf( "name: %s age: %d\n", (*(p_map+i) ).name, (*(p_map+i) ).age );


    }

    munmap(p_map, sizeof(people) * 10);

    close(fd);
    return 0;
}