The f_open function creates a file object to be used to access the file.
FRESULT f_open ( FIL* FileObject, /* Pointer to the blank file object structure */ const char* FileName, /* Pointer to the file neme */ BYTE ModeFlags /* 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, the function creates the new file. |
FA_CREATE_NEW | Creates a new file. The function fails if the file is already existing. |
FA_CREATE_ALWAYS | Creates a new file. If the file is existing, it is truncated and overwritten. |
The created file object is used for subsequent calls to refer to the file. When close an open file object, use f_close function. If modified file is not closed, the file may be collapsed.
Before using any file function, a work area (file system object) must be given to the logical drive with f_mount function. All file functions can work after this procedure.
The mode flags, FA_WRITE, FA_CREATE_ALWAYS, FA_CREATE_NEW, FA_OPEN_ALWAYS, are not available in read-only configuration.
void main () { FATFS fs; // Work area (file system object) for logical drive FIL fsrc, fdst; // file objects BYTE buffer[4096]; // file copy buffer FRESULT res; // FatFs function common result code UINT br, bw; // File R/W count // Register a work area for logical drive 0 f_mount(0, &fs); // Open source file res = f_open(&fsrc, "srcfile.dat", FA_OPEN_EXISTING | FA_READ); if (res) die(res); // Create destination file res = f_open(&fdst, "dstfile.dat", FA_CREATE_ALWAYS | FA_WRITE); if (res) die(res); // Copy source to destination for (;;) { res = f_read(&fsrc, buffer, sizeof(buffer), &br); if (res || br == 0) break; // error or eof res = f_write(&fdst, buffer, br, &bw); if (res || bw < br) break; // error or disk full } // Close all files f_close(&fsrc); f_close(&fdst); // Unregister a work area before discard it f_mount(0, NULL); }