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<title>FatFs - f_write</title>
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<div class="para">
<h2>f_write</h2>
<p>The f_write writes data to a file.</p>
<pre>
FRESULT f_write (
FIL* <em>FileObject</em>, <span class="c">/* Pointer to the file object structure */</span>
const void* <em>Buffer</em>, <span class="c">/* Pointer to the data to be written */</span>
UINT <em>ByteToWrite</em>, <span class="c">/* Number of bytes to write */</span>
UINT* <em>ByteWritten</em> <span class="c">/* Pointer to the variable to return number of bytes written */</span>
);
</pre>
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<div class="para">
<h4>Parameters</h4>
<dl class="par">
<dt>FileObject</dt>
<dd>Pointer to the open file object structure.</dd>
<dt>Buffer</dt>
<dd>Pointer to the data to be written.</dd>
<dt>ByteToWrite</dt>
<dd>Specifies number of bytes to write in range of UINT.</dd>
<dt>ByteWritten</dt>
<dd>Pointer to the UINT variable to return the number of bytes written. The value is always valid after the function call regardless of the result.</dd>
</dl>
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<div class="para">
<h4>Return Values</h4>
<dl class="ret">
<dt>FR_OK (0)</dt>
<dd>The function succeeded.</dd>
<dt>FR_DENIED</dt>
<dd>The function denied due to the file has been opened in non-write mode.</dd>
<dt>FR_DISK_ERR</dt>
<dd>The function failed due to an error in the disk function.</dd>
<dt>FR_INT_ERR</dt>
<dd>The function failed due to a wrong FAT structure or an internal error.</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_INVALID_OBJECT</dt>
<dd>The file object is invalid.</dd>
</dl>
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<div class="para">
<h4>Description</h4>
<p>The read/write pointer in the file object is increased in number of bytes written. After the function succeeded, <tt>*ByteWritten</tt> should be checked to detect the disk full. In case of <tt>*ByteWritten &lt; ByteToWrite</tt>, it means the volume got full during the write operation. The function can take a time when the volume is full or close to full.</p>
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<div class="para">
<h4>QuickInfo</h4>
<p>Available when <tt>_FS_READONLY == 0</tt>.</p>
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<h4>See Also</h4>
<p><tt><a href="open.html">f_open</a>, <a href="read.html">f_read</a>, <a href="putc.html">fputc</a>, <a href="puts.html">fputs</a>, <a href="printf.html">fprintf</a>, <a href="close.html">f_close</a>, <a href="sfile.html">FIL</a></tt></p>
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