文件系统学习 + Eric + 输出系统log

发布于 2018-07-18 21:43:25 浏览：1688 订阅该版

将系统 log 日志，保存为 csv 文件，存储到 SD 卡中，通过 winimage 提取出 csv 文件，可以通过 excel 打开；

log是通过rt_kprintf打印出来的，所以需要将在rt_kprintf函数中，将所有内容顺便往我们的csv文件中保持一份！

先编写csv一个函数：
```
void write_log_to_csv(const char* log_name, const char* log_buf)
{
	FILE *fp = fopen(log_name, "a+");
	if(fp == NULL)
		return;

fseek(fp, 0, SEEK_END);
	fwrite(log_buf, strlen(log_buf), 1, fp);
	fclose(fp);
}
```

在rt_kprintf函数中：
```
void rt_kprintf(const char *fmt, ...)
{
    va_list args;
    rt_size_t length;
    static char rt_log_buf[RT_CONSOLEBUF_SIZE];

va_start(args, fmt);
    /* the return value of vsnprintf is the number of bytes that would be
     * written to buffer had if the size of the buffer been sufficiently
     * large excluding the terminating null byte. If the output string
     * would be larger than the rt_log_buf, we have to adjust the output
     * length. */
    length = rt_vsnprintf(rt_log_buf, sizeof(rt_log_buf) - 1, fmt, args);
    if (length > RT_CONSOLEBUF_SIZE - 1)
        length = RT_CONSOLEBUF_SIZE - 1;
#ifdef RT_USING_DEVICE
    if (_console_device == RT_NULL)
    {
        rt_hw_console_output(rt_log_buf);
    }
    else
    {
        rt_uint16_t old_flag = _console_device->open_flag;

_console_device->open_flag |= RT_DEVICE_FLAG_STREAM;
        rt_device_write(_console_device, 0, rt_log_buf, length);
        _console_device->open_flag = old_flag;
    }

//添加log函数
	{
		extern int fs_system_init;//文件系统标志位，初始化完成后才工作，不然会出现下图错误
		extern void write_log_to_csv(const char* log_name, const char* log_buf);

if(fs_system_init == 1)
			write_log_to_csv("log.csv", rt_log_buf);
	}
#else
    rt_hw_console_output(rt_log_buf);
#endif
    va_end(args);
}
``` 
![1.png](/uploads/201807/18/214246teexau02fn2eenlu.png)
```
int fs_system_init = 0;

int mnt_init(void)
{
    rt_thread_delay(RT_TICK_PER_SECOND);

if (dfs_mount("sd0", "/", "elm", 0, 0) == 0)
    {
        rt_kprintf("file system initialization done!<br>");
    }
	
	fs_system_init = 1;

return 0;
}
```
运行情况：
![2.png](/uploads/201807/18/214247jxx5acc2micnz5o9.png)

![3.png](/uploads/201807/18/214247bn2hcs9yucnrs4lf.png)

![4.png](/uploads/201807/18/214247mpeyruvy9cunra3h.png)