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<title>FatFs - f_open</title>
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<div class="para">
<h2>f_open</h2>
<p>The f_open function creates a <em>file object</em> to be used to access the file.</p>
<pre>
FRESULT f_open (
FIL* <em>FileObject</em>, /* Pointer to the blank file object structure */
const char* <em>FileName</em>, /* Pointer to the file neme */
BYTE <em>ModeFlags</em> /* Mode flags */
);
</pre>
</div>
<div class="para">
<h4>Parameters</h4>
<dl class="par">
<dt>FileObject</dt>
<dd>Pointer to the file object structure to be created. After the f_open funciton succeeded, the file can be accessed with the file object structure until it is closed.</dd>
<dt>FileName</dt>
<dd>Pointer to a null-terminated string that specifies the <a href="filename.html">file name</a> to create or open.</dd>
<dt>ModeFlags</dt>
<dd>Specifies the type of access and open method for the file. It is specified by a combination of following flags.<br>
<table class="lst">
<tr><th>Value</th><th>Description</th></tr>
<tr><td>FA_READ</td><td>Specifies read access to the object. Data can be read from the file.<br>Combine with FA_WRITE for read-write access.</td></tr>
<tr><td>FA_WRITE</td><td>Specifies write access to the object. Data can be written to the file.<br>Combine with FA_READ for read-write access.</td></tr>
<tr><td>FA_OPEN_EXISTING</td><td>Opens the file. The function fails if the file is not existing.</td></tr>
<tr><td>FA_CREATE_ALWAYS</td><td>Creates a new file. If the file is existing, it is truncated and overwritten.</td></tr>
<tr><td>FA_OPEN_ALWAYS</td><td>Opens the file, if it is existing. If not, the function creates the new file.</td></tr>
</table>
</dd>
</dl>
</div>
<div class="para">
<h4>Return Values</h4>
<dl class="ret">
<dt>FR_OK (0)</dt>
<dd>The function succeeded and the file object is valid.</dd>
<dt>FR_NO_FILE</dt>
<dd>Could not find the file.</dd>
<dt>FR_NO_PATH</dt>
<dd>Could not find the path.</dd>
<dt>FR_INVALID_NAME</dt>
<dd>The file name is invalid.</dd>
<dt>FR_INVALID_DRIVE</dt>
<dd>The drive number is invalid.</dd>
<dt>FR_DENIED</dt>
<dd>The required access was denied due to any of following reasons: write mode open of a file that has read-only attribute, file creation under existing a same name directory or read-only file, cannot be created due to the directory table or disk full.</dd>
<dt>FR_NOT_READY</dt>
<dd>The disk drive cannot work due to no medium in the drive or any other reason.</dd>
<dt>FR_WRITE_PROTECTED</dt>
<dd>Write mode open or creation under the medium is write protected.</dd>
<dt>FR_RW_ERROR</dt>
<dd>Any error occured in low level disk I/O.</dd>
<dt>FR_NOT_ENABLED</dt>
<dd>The logical drive has no work area.</dd>
<dt>FR_NO_FILESYSTEM</dt>
<dd>There is no valid FAT partition on the disk.</dd>
</dl>
</div>
<div class="para">
<h4>Description</h4>
<p>The created file object is used for subsequent calls to refer to the file. When close an open file object, use <a href="close.html">f_close</a> function.</p>
<p>Before using any file function, work area (file system object) must be given to each logical drive with <a href="mount.html">f_mount</a> function. All file functions can work after this procedure.</p>
<p>Flags <tt>FA_WRITE, FA_CREATE_ALWAYS, FA_OPEN_ALWAYS</tt> are not supported in read-only configuration.</p>
</div>
<div class="para">
<h4>Example (File Copy)</h4>
<pre>
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
WORD br, bw; // File R/W count
// Register a work area to 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);
}
</pre>
</div>
<div class="para">
<h4>References</h4>
<p><tt><a href="read.html">f_read</a>, <a href="write.html">f_write</a>, <a href="close.html">f_close</a>, <a href="sfile.html">FIL</a>, <a href="sfatfs.html">FATFS</a></tt></p>
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