7天rtos网络编程 day1-2 作业2

发布于 2018-10-16 01:38:51 浏览：1603 订阅该版

* 本帖最后由 wo4fisher 于 2018-10-16 15:22 编辑 *

要求：打开文件1.txt 文件内容为"123456789"，修改为"abc456789"
思路：在源例子的基础上进行代码修改，文件路径：rt-thread\bsp\qemu-vexpress-a9\packages\filesystem_samples-latest，里边任意一个sample基础上进行修改。
 创建文件，写制定内容"123456789"，关闭；打开文件，读出内容，保存到缓存，关闭文件；修改缓存内容"abc456789"；打开文件，写入新内容，关闭文件。在终端上用相应的命令显示文件及目录内容。
步骤：同上；
```#include <rtthread.h>
#include <dfs_posix.h> /* 当需要使用文件操作时，需要包含这个头文件 */
#define TEST_FN "/test.txt"

/* 测试用的数据和缓冲 */
static char test_data[]="123456789",buffer[100];

static void mkdir_sample(void)
{
         int fd;
        int index, length;

/* 只写 & 创建 打开 */
 fd = open(TEST_FN, O_WRONLY | O_CREAT | O_TRUNC, 0);
 rt_kprintf("open ");
 if (fd >= 0)
 {
 /* 写入初始数据 */
 length = write(fd, test_data, sizeof(test_data));
 /* 关闭文件 */
 close(fd);
rt_kprintf("close "); 
 }
 else
 {
 rt_kprintf("open file for write failed ");
 return;
 }

/* 写读打开进行数据读取 */
 fd = open(TEST_FN, O_RDONLY, 0);
 rt_kprintf("open REONLY ");
 if (fd < 0)
 {
 rt_kprintf("check: open file for read failed ");
 return;
 }

/* 读取数据(应该为第一次写入的数据) */
 length = read(fd, buffer, sizeof(buffer));
 rt_kprintf("second read length=%d ",length);
/* if (length != sizeof(test_data))
 {
 rt_kprintf("check: read file failed ");
 close(fd);
 return;
 } */
 close(fd);
 rt_kprintf("%s ",buffer);
 /* 修改123为abc */
 for (index = 0; index < 3; index ++)
 {
 buffer[index]='a'+index;
 }
 rt_kprintf("%s ",buffer);
 /* 第二次写数据*/
 fd = open(TEST_FN, O_WRONLY, 0);
 rt_kprintf("open ");
 length = write(fd, buffer, length);
 rt_kprintf("second write end ");
/* if (length != sizeof(buffer))
 {
 rt_kprintf("check: read file failed ");
 close(fd);
 return;
 } */
 /* 检查数据完毕，关闭文件 */
 close(fd);
 /* 打印结果 */
 rt_kprintf("read/write done. ");
}
/* 导出到 msh 命令列表中 */
MSH_CMD_EXPORT(mkdir_sample, mkdir sample);```结果：
``` \ | /
- RT - Thread Operating System
 / | \ 3.1.0 build Oct 16 2018
 2006 - 2018 Copyright by rt-thread team
lwIP-2.0.2 initialized!
[I/SAL_SOC] Socket Abstraction Layer initialize success.
SD card capacity 65280 KB
switching card to high speed failed
probe mmcsd block device!
found part[0], begin: 32256, size: 63.988MB
file system initialization done!
hello rt-thread
msh />ls
Directory /:
17107.png 1035935
2018-09-30_125320.png278913
text1.txt 12
test.txt 10
dir_test <DIR>
msh />cat test.txt
abc456789msh />rm test.txt
msh />ls
Directory /:
17107.png 1035935
2018-09-30_125320.png278913
text1.txt 12
dir_test <DIR>
msh />mkdir_sample
open
close
open REONLY
second read length=10
123456789
abc456789
open
second write end
read/write done.
msh />cat test.txt
abc456789msh />```![2018-10-16_151846.png](/uploads/201810/16/152244xtc2aaczkad9tvov.png)