RT-Thread-ulog存到成文件，供后续查询RT-Thread问答社区

ulog存到成文件，供后续查询

发布于 2024-10-24 14:26:29 浏览：195 订阅该版

使用RT-Thread过程做些笔记，现在找到ulog操作资料有些旧了

1、我已经做完DFS文件系统，实现文件可以创建删除等，下图log文件存放在filesystem
![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20241024/39e59abd981dde3d0e2987abb2a60312.png.webp)
2、ulog按照官方资料操作，可以实现打印，ulog配置
![1.png](https://oss-club.rt-thread.org/uploads/20241024/5feb4f05e14f0801852bb69ffa8bdf37.png)
![2.png](https://oss-club.rt-thread.org/uploads/20241024/e24fbac5a97b99537c8381868212091c.png)
3、按照官方资料是文件后端需要注册再使能，注意设置路径且需要分配内存，这里分配512KB,是一个log文件大小

```c
/* 创建文件后端 */
#define FILE_SIZE 512 * 1024   //设置单个文件大小
#define BUFF_SIZE 512          //设备缓存区大小

/* 文件后端初始化 */
int ulog_fat_file_backend_init(void)
{
	int ret=0;
	struct ulog_file_be *be;
	
	/* 分配内存 */
	be = (struct ulog_file_be *)rt_malloc(sizeof(struct ulog_file_be));
	if (be == NULL)
	{
			LOG_E("Failed to allocate memory for ulog file backend");
			return -RT_ENOMEM;
	}

/* 清零内存 */
	rt_memset(be, 0, sizeof(struct ulog_file_be));
	
	strcpy(be->parent.name, "log");
	strcpy(be->cur_log_file_path, "/log");
	ret = ulog_file_backend_init(be, be->parent.name, be->cur_log_file_path, 10, FILE_SIZE, BUFF_SIZE);
	if(ret != 0)
	{
		LOG_E("ulog file init error");
	}
	
	ulog_file_backend_enable(be);

return 0;
}
INIT_APP_EXPORT(ulog_fat_file_backend_init);
```

4、注册后系统初始化单前当个文件存满会存转存到`log_0 ~ log_10`文件

```c
static rt_bool_t ulog_file_rotate(struct ulog_file_be *be)
{
#define SUFFIX_LEN          10
    /* mv xxx_n-1.log => xxx_n.log, and xxx.log => xxx_0.log */
    static char old_path[ULOG_FILE_PATH_LEN], new_path[ULOG_FILE_PATH_LEN];
    int index = 0, err = 0, file_fd = 0;
    rt_bool_t result = RT_FALSE;
    size_t base_len = 0;

rt_snprintf(old_path, ULOG_FILE_PATH_LEN, "%s/%s", be->cur_log_dir_path, be->parent.name);
    rt_snprintf(new_path, ULOG_FILE_PATH_LEN, "%s/%s", be->cur_log_dir_path, be->parent.name);
    base_len = rt_strlen(be->cur_log_dir_path) + rt_strlen(be->parent.name) + 1;

if (be->cur_log_file_fd >= 0)
    {
        close(be->cur_log_file_fd);
    }

for (index = be->file_max_num - 2; index >= 0; --index)
    {
        rt_snprintf(old_path + base_len, SUFFIX_LEN, index ? "_%d.log" : ".log", index - 1);
        rt_snprintf(new_path + base_len, SUFFIX_LEN, "_%d.log", index);
        /* remove the old file */
        if ((file_fd = open(new_path, O_RDONLY)) >= 0)
        {
            close(file_fd);
            unlink(new_path);
        }
        /* change the new log file to old file name */
        if ((file_fd = open(old_path , O_RDONLY)) >= 0)
        {
            close(file_fd);
            err = dfs_file_rename(old_path, new_path);
        }

if (err < 0)
        {
            result = RT_FALSE;
            goto __exit;
        }

result = RT_TRUE;
    }

__exit:
    /* reopen the file */
    be->cur_log_file_fd = open(be->cur_log_file_path, O_CREAT | O_RDWR | O_APPEND);

return result;
}
```

5、存好的日志，可以通过cat log.log查看下
![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20241024/d266c231030d9db6e0e355d59f2bd3c0.png.webp)