# Return Code of the File Functions

On the FatFs API, most of file functions return common result code as enum type `FRESULT`. When a function succeeded, it returns zero, otherwise returns non-zero value that indicates type of error.

FR_OK (0)
  The function succeeded.
FR_DISK_ERR
  An unrecoverable hard error occured in the lower layer, `disk_read()`, `disk_write()` or `disk_ioctl()` function.
  Note that if once this error occured at any operation to an open file, the file object is aborted and all operations to the file except for close will be rejected.
FR_INT_ERR
  Assertion failed. An insanity is detected in the internal process. One of the following possibilities is suspected.
  - Work area (file system object, file object or etc...) is broken by stack overflow or any other application. This is the reason in most case.
  - There is any error of the FAT structure on the volume.
  Note that if once this error occured at any operation to an open file, the file object is aborted and all operations to the file except for close will be rejected.
FR_NOT_READY
  The disk drive cannot work due to incorrect medium removal or `disk_initialize()` function failed.
FR_NO_FILE
  Could not find the file.
FR_NO_PATH
  Could not find the path.
FR_INVALID_NAME
  The given string is invalid as the path name.
FR_DENIED
  The required access was denied due to one of the following reasons:
  - Write mode open against the read-only file.
  - Deleting the read-only file or directory.
  - Deleting the non-empty directory or current directory.
  - Reading the file opened without `FA_READ` flag.
  - Any modification to the file opened without `FA_WRITE` flag.
  - Could not create the file or directory due to the directory table is full.
  - Could not create the directory due to the volume is full.
FR_EXIST
  Name collision. Any object that has the same name is already existing.
FR_INVALID_OBJECT
  The file/directory object structure is invalid or a null pointer is given. All open objects of the logical drive are invalidated by the voulme mount process.
FR_WRITE_PROTECTED
  Any write mode action against the write-protected media.
FR_INVALID_DRIVE
  Invalid drive number is specified in the path name. A null pointer is given as the path name. (Related option: `_VOLUMES`)
FR_NOT_ENABLED
  Work area for the logical drive has not been registered by `f_mount()` function.
FR_NO_FILESYSTEM
  There is no valid FAT volume on the drive.
FR_MKFS_ABORTED
  The `f_mkfs()` function aborted before start in format due to a reason as follows:
  - The disk/partition size is too small.
  - Not allowable cluster size for this disk. This can occure when number of clusters gets near the boundaries of FAT sub-types.
  - There is no partition related to the logical drive. (Related option: `_MULTI_PARTITION`)
FR_TIMEOUT
  The function was canceled due to a timeout of thread-safe control. (Related option: `_TIMEOUT`)
FR_LOCKED
  The operation to the object was rejected by file sharing control. (Related option: `_FS_LOCK`)
FR_NOT_ENOUGH_CORE
  Not enough memory for the operation. There is one of the following reasons:
  - Could not allocate a memory for LFN working buffer. (Related option: `_USE_LFN`)
  - Size of the given CLMT buffer is insufficient for the file fragments.
FR_TOO_MANY_OPEN_FILES
  Number of open objects has been reached maximum value and no more object can be opened. (Related option: `_FS_LOCK`)
FR_INVALID_PARAMETER
  The given parameter is invalid or there is any inconsistent.