The f_open function creates a file object to be used to access the file.
FRESULT f_open ( FIL* fp, /* [OUT] Pointer to the file object structure */ const TCHAR* path, /* [IN] File name */ BYTE mode /* [IN] Mode flags */ );
| Value | Description |
|---|---|
| FA_READ | Specifies read access to the object. Data can be read from the file. Combine with FA_WRITE for read-write access. |
| FA_WRITE | Specifies write access to the object. Data can be written to the file. Combine with FA_READ for read-write access. |
| FA_OPEN_EXISTING | Opens the file. The function fails if the file is not existing. (Default) |
| FA_OPEN_ALWAYS | Opens the file if it is existing. If not, a new file is created. To append data to the file, use f_lseek() function after file open in this method. |
| FA_CREATE_NEW | Creates a new file. The function fails with FR_EXIST if the file is existing. |
| FA_CREATE_ALWAYS | Creates a new file. If the file is existing, it will be truncated and overwritten. |
FR_OK, FR_DISK_ERR, FR_INT_ERR, FR_NOT_READY, FR_NO_FILE, FR_NO_PATH, FR_INVALID_NAME, FR_DENIED, FR_EXIST, FR_INVALID_OBJECT, FR_WRITE_PROTECTED, FR_INVALID_DRIVE, FR_NOT_ENABLED, FR_NO_FILESYSTEM, FR_TIMEOUT, FR_LOCKED, FR_NOT_ENOUGH_CORE, FR_TOO_MANY_OPEN_FILES
After f_open() function succeeded, the file object is valid. The file object is used for subsequent read/write functions to identify the file. To close an open file, use f_close() function. If the file is modified and not closed properly, the file data will be collapsed.
If duplicated file open is needed, read here carefully. However duplicated open of a file with write mode flag is always prohibited.
Before using any file function, a work area (file system object) must be registered to the logical drive with f_mount() function. All API functions except for f_fdisk() function can work after this procedure.
Always available. The mode flags, FA_WRITE, FA_CREATE_ALWAYS, FA_CREATE_NEW and FA_OPEN_ALWAYS, are not available when _FS_READONLY == 1.
/* Read a text file and display it */ FATFS FatFs; /* Work area (file system object) for logical drive */ int main (void) { FIL fil; /* File object */ char line[82]; /* Line buffer */ FRESULT fr; /* FatFs return code */ /* Register work area to the default drive */ f_mount(&FatFs, "", 0); /* Open a text file */ fr = f_open(&fil, "message.txt", FA_READ); if (fr) return (int)fr; /* Read all lines and display it */ while (f_gets(line, sizeof line, &fil)) printf(line); /* Close the file */ f_close(&fil); return 0; }
/* Copy a file "file.bin" on the drive 1 to drive 0 */ int main (void) { FATFS fs[2]; /* Work area (file system object) for logical drives */ FIL fsrc, fdst; /* File objects */ BYTE buffer[4096]; /* File copy buffer */ FRESULT fr; /* FatFs function common result code */ UINT br, bw; /* File read/write count */ /* Register work area for each logical drive */ f_mount(&fs[0], "0:", 0); f_mount(&fs[1], "1:", 0); /* Open source file on the drive 1 */ fr = f_open(&fsrc, "1:file.bin", FA_OPEN_EXISTING | FA_READ); if (fr) return (int)fr; /* Create destination file on the drive 0 */ fr = f_open(&fdst, "0:file.bin", FA_CREATE_ALWAYS | FA_WRITE); if (fr) return (int)fr; /* Copy source to destination */ for (;;) { fr = f_read(&fsrc, buffer, sizeof buffer, &br); /* Read a chunk of source file */ if (fr || br == 0) break; /* error or eof */ fr = f_write(&fdst, buffer, br, &bw); /* Write it to the destination file */ if (fr || bw < br) break; /* error or disk full */ } /* Close open files */ f_close(&fsrc); f_close(&fdst); /* Unregister work area prior to discard it */ f_mount(NULL, "0:", 0); f_mount(NULL, "1:", 0); return (int)fr; }