系统 循环写入，读取结构体

写入结构体

typedef struct student
{
    char name[20];
    int num;
    char sex[10];
    int score;
}student;
int main(void)
{
    int fd = -1;
    fd = open("stu.info",O_WRONLY| O_CREAT, S_IRWXU|S_IWGRP|S_IROTH);
    if (-1 == fd)
    {
        printf("open file failed....\n");
        printf("errno = %d\n",errno);
        printf("error:%s\n",strerror(errno));   
    }
    else
    {
        printf("open file ok...\n");
        int ret =-1;
        student  caBuf[3]={{"alex1",100,"boy",81},
                {"alex2",101,"boy",81},
                {"alex3",102,"boy",81}};
        int i = 0;
        for(;i<3;i++)
        {
            ret = write(fd,caBuf+i,sizeof(student));    
        }
        
        if(-1 == ret) 
        {
            printf("write error:%s\n",strerror(errno));
        }
        else
        {
            printf("write %d bytes to file \n",ret);
        }
        close(fd);//关闭文件描述符
    }
    return 0;
}

循环读取结果体

#include <stdio.h>
#include <unistd.h>  //write()
#include <errno.h>   //errno
#include <string.h>  //strerror()
/*open()*/
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

#define PER_WRITE_BYTES 4096
typedef struct student
{
    char name[20];
    int num;
    char sex[10];
    int score;
}student;
int myOpen(const char *pathname)
{
    int fd  = -1;
    if (NULL != pathname)
    {
        fd = open(pathname, O_RDONLY | O_CREAT 
                  , S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
        if (-1 == fd)
        {
            printf("open error: %s\n", strerror(errno));
        }
    }
    return fd;
}
int main(void)
{
    int fd = -1;
    fd = myOpen("stu.info");
    if (-1 != fd)
    {
        student stu;
        memset(&stu,'\0',sizeof(student));//初始话里面的内容
        while(1)
        {
                int ret = -1;
                ret = read(fd, &stu, sizeof(student));
                if(ret == 0)
                {
                        printf("touch the end\n");
                        break;
                }
                else if (-1 != ret)
                {
                        printf("name:%s,num:%d,sex:%s,score:%d\n",
  stu.name,stu.num,stu.sex,stu.score);
                        // printf("%s\n", caBuf);
                }
                else
                {
                        printf("read error:%s\n", strerror(errno));
                        break;
                }
        }
        close(fd);
    }


    return 0;
}