Filesystem ========== Flash layout ------------ Even though file system is stored on the same flash chip as the program, programming new sketch will not modify file system contents. This allows to use file system to store sketch data, configuration files, or content for Web server. The following diagram illustrates flash layout used in Arduino environment: :: |--------------|-------|---------------|--|--|--|--|--| ^ ^ ^ ^ ^ Sketch OTA update File system EEPROM WiFi config (SDK) File system size depends on the flash chip size. Depending on the board which is selected in IDE, the following table shows options for flash size. Another option called ``Mapping defined by Hardware and Sketch`` is available. It allows a sketch, not the user, to select FS configuration at boot according to flash chip size. This option is also enabled with this compilation define: ``-DFLASH_MAP_SUPPORT=1``. There are three possible configurations: - ``FLASH_MAP_OTA_FS``: largest available space for onboard FS, allowing OTA (noted 'OTA' in the table) - ``FLASH_MAP_MAX_FS``: largest available space for onboard FS (noted 'MAX' in the table) - ``FLASH_MAP_NO_FS``: no onboard FS Sketch can invoke a particular configuration by adding this line: .. code:: cpp FLASH_MAP_SETUP_CONFIG(FLASH_MAP_OTA_FS) void setup () { ... } void loop () { ... } +-------+--------------------------+----------------------------------------------------------+ | Board | Flash chip size (bytes) | File system size (bytes) | +=======+==========================+==========================================================+ | Any | 512KBytes | 32KB(OTA), 64KB, 128KB(MAX) | +-------+--------------------------+----------------------------------------------------------+ | Any | 1MBytes | 64KB(OTA), 128KB, 144KB, 160KB, 192KB, 256KB, 512KB(MAX) | +-------+--------------------------+----------------------------------------------------------+ | Any | 2MBytes | 64KB, 128KB, 256KB(OTA), 512KB, 1MB(MAX) | +-------+--------------------------+----------------------------------------------------------+ | Any | 4MBytes | 1MB, 2MB(OTA), 3MB(MAX) | +-------+--------------------------+----------------------------------------------------------+ | Any | 8MBytes | 6MB(OTA), 7MB(MAX) | +-------+--------------------------+----------------------------------------------------------+ | Any | 16MBytes | 14MB(OTA), 15MB(MAX) | +-------+--------------------------+----------------------------------------------------------+ **Note:** to use any of file system functions in the sketch, add the following include to the sketch: .. code:: cpp //#include "FS.h" // SPIFFS is declared #include "LittleFS.h" // LittleFS is declared //#include "SDFS.h" // SDFS is declared SPIFFS Deprecation Warning -------------------------- SPIFFS is currently deprecated and may be removed in future releases of the core. Please consider moving your code to LittleFS. SPIFFS is not actively supported anymore by the upstream developer, while LittleFS is under active development, supports real directories, and is many times faster for most operations. SPIFFS and LittleFS ------------------- There are two filesystems for utilizing the onboard flash on the ESP8266: SPIFFS and LittleFS. SPIFFS is the original filesystem and is ideal for space and RAM constrained applications that utilize many small files and care about static and dynamic wear levelling and don't need true directory support. Filesystem overhead on the flash is minimal as well. LittleFS is recently added and focuses on higher performance and directory support, but has higher filesystem and per-file overhead (4K minimum vs. SPIFFS' 256 byte minimum file allocation unit). They share a compatible API but have incompatible on-flash implementations, so it is important to choose one or the other per project as attempting to mount a SPIFFS volume under LittleFS may result in a format operation and definitely will not preserve any files, and vice-versa. The actual ``File`` and ``Dir`` objects returned from either filesystem behave in the same manner and documentation is applicable to both. To convert most applications from SPIFFS to LittleFS simply requires changing the ``SPIFFS.begin()`` to ``LittleFS.begin()`` and ``SPIFFS.open()`` to ``LittleFS.open()`` with the rest of the code remaining untouched. SDFS and SD ----------- FAT filesystems are supported on the ESP8266 using the old Arduino wrapper "SD.h" which wraps the "SDFS.h" filesystem transparently. Any commands discussed below pertaining to SPIFFS or LittleFS are applicable to SD/SDFS. For legacy applications, the classic SD filesystem may continue to be used, but for new applications, directly accessing the SDFS filesystem is recommended as it may expose additional functionality that the old Arduino SD filesystem didn't have. Note that in earlier releases of the core, using SD and SPIFFS in the same sketch was complicated and required the use of ``NO_FS_GLOBALS``. The current design makes SD, SDFS, SPIFFS, and LittleFS fully source compatible and so please remove any ``NO_FS_GLOBALS`` definitions in your projects when updgrading core versions. SPIFFS file system limitations ------------------------------ The SPIFFS implementation for ESP8266 had to accommodate the constraints of the chip, among which its limited RAM. `SPIFFS `__ was selected because it is designed for small systems, but that comes at the cost of some simplifications and limitations. First, behind the scenes, SPIFFS does not support directories, it just stores a "flat" list of files. But contrary to traditional filesystems, the slash character ``'/'`` is allowed in filenames, so the functions that deal with directory listing (e.g. ``openDir("/website")``) basically just filter the filenames and keep the ones that start with the requested prefix (``/website/``). Practically speaking, that makes little difference though. Second, there is a limit of 32 chars in total for filenames. One ``'\0'`` char is reserved for C string termination, so that leaves us with 31 usable characters. Combined, that means it is advised to keep filenames short and not use deeply nested directories, as the full path of each file (including directories, ``'/'`` characters, base name, dot and extension) has to be 31 chars at a maximum. For example, the filename ``/website/images/bird_thumbnail.jpg`` is 34 chars and will cause some problems if used, for example in ``exists()`` or in case another file starts with the same first 31 characters. **Warning**: That limit is easily reached and if ignored, problems might go unnoticed because no error message will appear at compilation nor runtime. For more details on the internals of SPIFFS implementation, see the `SPIFFS readme file `__. LittleFS file system limitations -------------------------------- The LittleFS implementation for the ESP8266 supports filenames of up to 31 characters + terminating zero (i.e. ``char filename[32]``), and as many subdirectories as space permits. Filenames are assumed to be in the root directory if no initial "/" is present. Opening files in subdirectories requires specifying the complete path to the file (i.e. ``open("/sub/dir/file.txt");``). Subdirectories are automatically created when you attempt to create a file in a subdirectory, and when the last file in a subdirectory is removed the subdirectory itself is automatically deleted. This is because there was no ``mkdir()`` method in the existing SPIFFS filesystem. Unlike SPIFFS, the actual file descriptors are allocated as requested by the application, so in low memory conditions you may not be able to open new files. Conversely, this also means that only file descriptors used will actually take space on the heap. Because there are directories, the ``openDir`` method behaves differently than SPIFFS. Whereas SPIFFS will return files in "subdirectories" when you traverse a ``Dir::next()`` (because they really aren't subdirs but simply files with "/"s in their names), LittleFS will only return files in the specific subdirectory. This mimics the POSIX behavior for directory traversal most C programmers are used to. Uploading files to file system ------------------------------ *ESP8266FS* is a tool which integrates into the Arduino IDE. It adds a menu item to *Tools* menu for uploading the contents of sketch data directory into ESP8266 flash file system. **Warning**: Due to the move from the obsolete esptool-ck.exe to the supported esptool.py upload tool, upgraders from pre 2.5.1 will need to update the ESP8266FS tool referenced below to 0.5.0 or later. Prior versions will fail with a "esptool not found" error because they don't know how to use esptool.py. - Download the tool: https://github.com/esp8266/arduino-esp8266fs-plugin/releases/download/0.5.0/ESP8266FS-0.5.0.zip - In your Arduino sketchbook directory, create ``tools`` directory if it doesn't exist yet. - Unpack the tool into ``tools`` directory (the path will look like ``/Arduino/tools/ESP8266FS/tool/esp8266fs.jar``) If upgrading, overwrite the existing JAR file with the newer version. - Restart Arduino IDE. - Open a sketch (or create a new one and save it). - Go to sketch directory (choose Sketch > Show Sketch Folder). - Create a directory named ``data`` and any files you want in the file system there. - Make sure you have selected a board, port, and closed Serial Monitor. - If your board requires you to press a button (or other action) to enter bootload mode for flashing a sketch, do that now. - Select Tools > ESP8266 Sketch Data Upload. This should start uploading the files into ESP8266 flash file system. When done, IDE status bar will display ``SPIFFS Image Uploaded`` message. *ESP8266LittleFS* is the equivalent tool for LittleFS. - Download the 2.6.0 or later version of the tool: https://github.com/earlephilhower/arduino-esp8266littlefs-plugin/releases - Install as above - To upload a LittleFS filesystem use Tools > ESP8266 LittleFS Data Upload File system object (SPIFFS/LittleFS/SD/SDFS) -------------------------------------------- setConfig ~~~~~~~~~ .. code:: cpp SPIFFSConfig cfg; cfg.setAutoFormat(false); SPIFFS.setConfig(cfg); This method allows you to configure the parameters of a filesystem before mounting. All filesystems have their own ``*Config`` (i.e. ``SDFSConfig`` or ``SPIFFSConfig`` with their custom set of options. All filesystems allow explicitly enabling/disabling formatting when mounts fail. If you do not call this ``setConfig`` method before perforing ``begin()``, you will get the filesystem's default behavior and configuration. By default, SPIFFS will autoformat the filesystem if it cannot mount it, while SDFS will not. begin ~~~~~ .. code:: cpp SPIFFS.begin() or LittleFS.begin() This method mounts file system. It must be called before any other FS APIs are used. Returns *true* if file system was mounted successfully, false otherwise. With no options it will format SPIFFS if it is unable to mount it on the first try. Note that both methods will automatically format the filesystem if one is not detected. This means that if you attempt a ``SPIFFS.begin()`` on a LittleFS filesystem you will lose all data on that filesystem, and vice-versa. end ~~~ .. code:: cpp SPIFFS.end() or LittleFS.end() This method unmounts the file system. Use this method before updating the file system using OTA. format ~~~~~~ .. code:: cpp SPIFFS.format() or LittleFS.format() Formats the file system. May be called either before or after calling ``begin``. Returns *true* if formatting was successful. open ~~~~ .. code:: cpp SPIFFS.open(path, mode) or LittleFS.open(path, mode) Opens a file. ``path`` should be an absolute path starting with a slash (e.g. ``/dir/filename.txt``). ``mode`` is a string specifying access mode. It can be one of "r", "w", "a", "r+", "w+", "a+". Meaning of these modes is the same as for ``fopen`` C function. :: r Open text file for reading. The stream is positioned at the beginning of the file. r+ Open for reading and writing. The stream is positioned at the beginning of the file. w Truncate file to zero length or create text file for writing. The stream is positioned at the beginning of the file. w+ Open for reading and writing. The file is created if it does not exist, otherwise it is truncated. The stream is positioned at the beginning of the file. a Open for appending (writing at end of file). The file is created if it does not exist. The stream is positioned at the end of the file. a+ Open for reading and appending (writing at end of file). The file is created if it does not exist. The initial file position for reading is at the beginning of the file, but output is always appended to the end of the file. Returns *File* object. To check whether the file was opened successfully, use the boolean operator. .. code:: cpp File f = SPIFFS.open("/f.txt", "w"); if (!f) { Serial.println("file open failed"); } exists ~~~~~~ .. code:: cpp SPIFFS.exists(path) or LittleFS.exists(path) Returns *true* if a file with given path exists, *false* otherwise. mkdir ~~~~~ .. code:: cpp LittleFS.mkdir(path) Returns *true* if the directory creation succeeded, *false* otherwise. rmdir ~~~~~ .. code:: cpp LittleFS.rmdir(path) Returns *true* if the directory was successfully removed, *false* otherwise. openDir ~~~~~~~ .. code:: cpp SPIFFS.openDir(path) or LittleFS.openDir(path) Opens a directory given its absolute path. Returns a *Dir* object. Please note the previous discussion on the difference in behavior between LittleFS and SPIFFS for this call. remove ~~~~~~ .. code:: cpp SPIFFS.remove(path) or LittleFS.remove(path) Deletes the file given its absolute path. Returns *true* if file was deleted successfully. rename ~~~~~~ .. code:: cpp SPIFFS.rename(pathFrom, pathTo) or LittleFS.rename(pathFrom, pathTo) Renames file from ``pathFrom`` to ``pathTo``. Paths must be absolute. Returns *true* if file was renamed successfully. gc ~~ .. code:: cpp SPIFFS.gc() Only implemented in SPIFFS. Performs a quick garbage collection operation on SPIFFS, possibly making writes perform faster/better in the future. On very full or very fragmented filesystems, using this call can avoid or reduce issues where SPIFFS reports free space but is unable to write additional data to a file. See `this discussion ` for more info. check ~~~~~ .. code:: cpp SPIFFS.begin(); SPIFFS.check(); Only implemented in SPIFFS. Performs an in-depth check of the filesystem metadata and correct what is repairable. Not normally needed, and not guaranteed to actually fix anything should there be corruption. info ~~~~ .. code:: cpp FSInfo fs_info; SPIFFS.info(fs_info); or LittleFS.info(fs_info); Fills `FSInfo structure <#filesystem-information-structure>`__ with information about the file system. Returns ``true`` if successful, ``false`` otherwise. Filesystem information structure -------------------------------- .. code:: cpp struct FSInfo { size_t totalBytes; size_t usedBytes; size_t blockSize; size_t pageSize; size_t maxOpenFiles; size_t maxPathLength; }; This is the structure which may be filled using FS::info method. - ``totalBytes`` — total size of useful data on the file system - ``usedBytes`` — number of bytes used by files - ``blockSize`` — filesystem block size - ``pageSize`` — filesystem logical page size - ``maxOpenFiles`` — max number of files which may be open simultaneously - ``maxPathLength`` — max file name length (including one byte for zero termination) info64 ~~~~~~ .. code:: cpp FSInfo64 fsinfo; SD.info(fsinfo); or LittleFS(fsinfo); Performs the same operation as ``info`` but allows for reporting greater than 4GB for filesystem size/used/etc. Should be used with the SD and SDFS filesystems since most SD cards today are greater than 4GB in size. setTimeCallback(time_t (\*cb)(void)) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ .. code:: cpp time_t myTimeCallback() { return 1455451200; // UNIX timestamp } void setup () { LittleFS.setTimeCallback(myTimeCallback); ... // Any files will now be made with Pris' incept date } The SD, SDFS, and LittleFS filesystems support a file timestamp, updated when the file is opened for writing. By default, the ESP8266 will use the internal time returned from ``time(NULL)`` (i.e. local time, not UTC, to conform to the existing FAT filesystem), but this can be overridden to GMT or any other standard you'd like by using ``setTimeCallback()``. If your app sets the system time using NTP before file operations, then you should not need to use this function. However, if you need to set a specific time for a file, or the system clock isn't correct and you need to read the time from an external RTC or use a fixed time, this call allows you do to so. In general use, with a functioning ``time()`` call, user applications should not need to use this function. Directory object (Dir) ---------------------- The purpose of *Dir* object is to iterate over files inside a directory. It provides multiple access methods. The following example shows how it should be used: .. code:: cpp Dir dir = SPIFFS.openDir("/data"); // or Dir dir = LittleFS.openDir("/data"); while (dir.next()) { Serial.print(dir.fileName()); if(dir.fileSize()) { File f = dir.openFile("r"); Serial.println(f.size()); } } next ~~~~ Returns true while there are files in the directory to iterate over. It must be called before calling ``fileName()``, ``fileSize()``, and ``openFile()`` functions. fileName ~~~~~~~~~ Returns the name of the current file pointed to by the internal iterator. fileSize ~~~~~~~~ Returns the size of the current file pointed to by the internal iterator. fileTime ~~~~~~~~ Returns the time_t write time of the current file pointed to by the internal iterator. fileCreationTime ~~~~~~~~~~~~~~~~ Returns the time_t creation time of the current file pointed to by the internal iterator. isFile ~~~~~~ Returns *true* if the current file pointed to by the internal iterator is a File. isDirectory ~~~~~~~~~~~ Returns *true* if the current file pointed to by the internal iterator is a Directory. openFile ~~~~~~~~ This method takes *mode* argument which has the same meaning as for ``SPIFFS/LittleFS.open()`` function. rewind ~~~~~~ Resets the internal pointer to the start of the directory. setTimeCallback(time_t (\*cb)(void)) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Sets the time callback for any files accessed from this Dir object via openNextFile. Note that the SD and SDFS filesystems only support a filesystem-wide callback and calls to ``Dir::setTimeCallback`` may produce unexpected behavior. File object ----------- ``SPIFFS/LittleFS.open()`` and ``dir.openFile()`` functions return a *File* object. This object supports all the functions of *Stream*, so you can use ``readBytes``, ``findUntil``, ``parseInt``, ``println``, and all other *Stream* methods. There are also some functions which are specific to *File* object. seek ~~~~ .. code:: cpp file.seek(offset, mode) This function behaves like ``fseek`` C function. Depending on the value of ``mode``, it moves current position in a file as follows: - if ``mode`` is ``SeekSet``, position is set to ``offset`` bytes from the beginning. - if ``mode`` is ``SeekCur``, current position is moved by ``offset`` bytes. - if ``mode`` is ``SeekEnd``, position is set to ``offset`` bytes from the end of the file. Returns *true* if position was set successfully. position ~~~~~~~~ .. code:: cpp file.position() Returns the current position inside the file, in bytes. size ~~~~ .. code:: cpp file.size() Returns file size, in bytes. name ~~~~ .. code:: cpp String name = file.name(); Returns short (no-path) file name, as ``const char*``. Convert it to *String* for storage. fullName ~~~~~~~~ .. code:: cpp // Filesystem: // testdir/ // file1 Dir d = LittleFS.openDir("testdir/"); File f = d.openFile("r"); // f.name() == "file1", f.fullName() == "testdir/file1" Returns the full path file name as a ``const char*``. getLastWrite ~~~~~~~~~~~~ Returns the file last write time, and only valid for files opened in read-only mode. If a file is opened for writing, the returned time may be indeterminate. getCreationTime ~~~~~~~~~~~~~~~ Returns the file creation time, if available. isFile ~~~~~~ .. code:: cpp bool amIAFile = file.isFile(); Returns *true* if this File points to a real file. isDirectory ~~~~~~~~~~~ .. code:: cpp bool amIADir = file.isDir(); Returns *true* if this File points to a directory (used for emulation of the SD.* interfaces with the ``openNextFile`` method). close ~~~~~ .. code:: cpp file.close() Close the file. No other operations should be performed on *File* object after ``close`` function was called. openNextFile (compatibiity method, not recommended for new code) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ .. code:: cpp File root = LittleFS.open("/"); File file1 = root.openNextFile(); File files = root.openNextFile(); Opens the next file in the directory pointed to by the File. Only valid when ``File.isDirectory() == true``. rewindDirectory (compatibiity method, not recommended for new code) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ .. code:: cpp File root = LittleFS.open("/"); File file1 = root.openNextFile(); file1.close(); root.rewindDirectory(); file1 = root.openNextFile(); // Opens first file in dir again Resets the ``openNextFile`` pointer to the top of the directory. Only valid when ``File.isDirectory() == true``. setTimeCallback(time_t (\*cb)(void)) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Sets the time callback for this specific file. Note that the SD and SDFS filesystems only support a filesystem-wide callback and calls to ``Dir::setTimeCallback`` may produce unexpected behavior.