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 | Meaning |
|---|---|
| FA_READ | Specifies read access to the object. Data can be read from the file. |
| 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_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. |
| FA_OPEN_ALWAYS | Opens the file if it is existing. If not, a new file will be created. |
| FA_OPEN_APPEND | Same as FA_OPEN_ALWAYS except read/write pointer is set end of the file. |
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
Before using any file function, a work area (file system object) needs to be registered to the logical drive with f_mount function. All API functions except for f_mkfs/f_fdisk function get ready to work after this procedure.
After f_open function succeeded, the file object is valid. The file object is used for subsequent operations to the file to identify the file. Open file must be closed prior to power down, media removal or re-mount, or the file can be collapsed. To close an open file, use f_close function.
If duplicated file open is needed, read here carefully. However duplicated open of a file with any write mode flag is always prohibited.
Always available. Only FA_READ and FA_OPEN_EXISTING are supported 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_READ); if (fr) return (int)fr; /* Create destination file on the drive 0 */ fr = f_open(&fdst, "0:file.bin", FA_WRITE | FA_CREATE_ALWAYS); 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; }