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<title>FatFs - f_read</title>
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<div class="para">
<h2>f_read</h2>
<p>The f_read function reads data from a file.</p>
<pre>
FRESULT f_read (
FIL* <em>FileObject</em>, /* Pointer to the file object structure */
void* <em>Buffer</em>, /* Pointer to the buffer to store read data */
UINT <em>ByteToRead</em>, /* Number of bytes to read */
UINT* <em>ByteRead</em> /* Pointer to the variable to return number of bytes read */
);
</pre>
</div>
<div class="para">
<h4>Parameters</h4>
<dl class="par">
<dt>FileObject</dt>
<dd>Pointer to the open file object.</dd>
<dt>Buffer</dt>
<dd>Pointer to the buffer to store read data</dd>
<dt>ByteToRead</dt>
<dd>Number of bytes to read in range of UINT.</dd>
<dt>ByteRead</dt>
<dd>Pointer to the UINT variable to return number of bytes read.</dd>
</dl>
</div>
<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-read 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>
</div>
<div class="para">
<h4>Description</h4>
<p>The file pointer of the file object increases in number of bytes read. After the function succeeded, <tt>*ByteRead</tt> should be checked to detect end of file. In case of <tt>*ByteRead < ByteToRead</tt>, it means the R/W pointer reached end of file during read operation.</p>
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<div class="para">
<h4>References</h4>
<p><tt><a href="open.html">f_open</a>, <a href="gets.html">fgets</a>, <a href="write.html">f_write</a>, <a href="close.html">f_close</a>, <a href="sfile.html">FIL</a></tt></p>
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