filesystem-sample/readwrite/readwrite_sample.c

/* 
 * Copyright (c) 2006-2018, RT-Thread Development Team 
 * 
 * SPDX-License-Identifier: Apache-2.0 
 * 
 * Change Logs: 
 * Date             Author      Notes
 * 
 */
/*
 * 代码清单：文件读写例子
 *
 * 这个例子演示了如何读写一个文件，特别是写的时候应该如何操作。
 */

#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.dat"

/* 测试用的数据和缓冲 */
static char test_data[120], buffer[120];

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

    /* 只写 & 创建 打开 */
    fd = open(TEST_FN, O_WRONLY | O_CREAT | O_TRUNC, 0);
    if (fd < 0)
    {
        rt_kprintf("open file for write failed\n");
        return;
    }

    /* 准备写入数据 */
    for (index = 0; index < sizeof(test_data); index ++)
    {
        test_data[index] = index + 48;
    }

    /* 写入数据 */
    length = write(fd, test_data, sizeof(test_data));
    if (length != sizeof(test_data))
    {
        rt_kprintf("write data failed\n");
        close(fd);
        return;
    }

    /* 关闭文件 */
    close(fd);

    /* 只写并在末尾添加打开 */
    fd = open(TEST_FN, O_WRONLY | O_CREAT | O_APPEND, 0);
    if (fd < 0)
    {
        rt_kprintf("open file for append write failed\n");
        return;
    }

    length = write(fd, test_data, sizeof(test_data));
    if (length != sizeof(test_data))
    {
        rt_kprintf("append write data failed\n");
        close(fd);          
        return;
    }
    /* 关闭文件 */
    close(fd);

    /* 只读打开进行数据校验 */
    fd = open(TEST_FN, O_RDONLY, 0);
    if (fd < 0)
    {
        rt_kprintf("check: open file for read failed\n");
        return;
    }

    /* 读取数据(应该为第一次写入的数据) */
    length = read(fd, buffer, sizeof(buffer));
    if (length != sizeof(buffer))
    {
        rt_kprintf("check: read file failed\n");
        close(fd);
        return;
    }

    /* 检查数据是否正确 */
    for (index = 0; index < sizeof(test_data); index ++)
    {
        if (test_data[index] != buffer[index])
        {
            rt_kprintf("check: check data failed at %d\n", index);
            close(fd);
            return;
        }
    }

    /* 读取数据(应该为第二次写入的数据) */
    length = read(fd, buffer, sizeof(buffer));
    if (length != sizeof(buffer))
    {
        rt_kprintf("check: read file failed\n");
        close(fd);
        return;
    }

    /* 检查数据是否正确 */
    for (index = 0; index < sizeof(test_data); index ++)
    {
        if (test_data[index] != buffer[index])
        {
            rt_kprintf("check: check data failed at %d\n", index);
            close(fd);
            return;
        }
    }

    /* 检查数据完毕，关闭文件 */
    close(fd);
    /* 打印结果 */
    rt_kprintf("read/write done.\n");
}
/* 导出到 msh 命令列表中 */
MSH_CMD_EXPORT(readwrite_sample, readwrite sample);