[嵌入式]物联网综合应用作业三

① vim write.c

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


struct student {
    char name[20];
    int id;
    int age;
    char sex;
};

int main(){
    struct student stu[3] = {{"学生0", 1, 19, 'G'},
                             {"学生1", 2, 20, 'M'},
                             {"学生2", 3, 21, 'M'}};

    int fd = open("./stu.dat",O_RDWR | O_CREAT,0644),i = 0,target;

    for (; i < 3; ++i) {
        write(fd,&stu[i],sizeof(stu[i]));
    }

    void *addr = mmap(NULL,sizeof(stu)*sizeof(stu[i]) , PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);

    if(addr == MAP_FAILED){
        perror("mmap failed");
        return -1;
    }

    struct student *p = addr;
    scanf("%d",&target);
    printf("%s age =%d\n", (p+target)->name ,(p+target)->age);

    munmap(addr, 56);
    close(fd);
    
    return 0;
}

②?gcc -o write write.c

③ ./write

4. 回车后输入 0-2 查询指定学生年龄