fatfs/doc/en/read.html

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   9 <title>FatFs - f_read</title>
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  13
  14 <div class="para func">
  15 <h2>f_read</h2>
  16 <p>The f_read function reads data from a file.</p>
  17 <pre>
  18 FRESULT f_read (
  19   FIL* <span class="arg">fp</span>,     <span class="c">/* [IN] File object */</span>
  20   void* <span class="arg">buff</span>,  <span class="c">/* [OUT] Buffer to store read data */</span>
  21   UINT <span class="arg">btr</span>,    <span class="c">/* [IN] Number of bytes to read */</span>
  22   UINT* <span class="arg">br</span>     <span class="c">/* [OUT] Number of bytes read */</span>
  23 );
  24 </pre>
  25 </div>
  26
  27 <div class="para arg">
  28 <h4>Parameters</h4>
  29 <dl class="par">
  30 <dt>fp</dt>
  31 <dd>Pointer to the open file object.</dd>
  32 <dt>buff</dt>
  33 <dd>Pointer to the buffer to store read data.</dd>
  34 <dt>btr</dt>
  35 <dd>Number of bytes to read in range of <tt>UINT</tt> type.</dd>
  36 <dt>br</dt>
  37 <dd>Pointer to the <tt>UINT</tt> variable to return number of bytes read. The value is always valid after the function call regardless of the result code.</dd>
  38 </dl>
  39 </div>
  40
  41
  42 <div class="para ret">
  43 <h4>Return Values</h4>
  44 <p>
  45 <a href="rc.html#ok">FR_OK</a>,
  46 <a href="rc.html#de">FR_DISK_ERR</a>,
  47 <a href="rc.html#ie">FR_INT_ERR</a>,
  48 <a href="rc.html#io">FR_INVALID_OBJECT</a>,
  49 <a href="rc.html#tm">FR_TIMEOUT</a>
  50 </p>
  51 </div>
  52
  53
  54 <div class="para desc">
  55 <h4>Description</h4>
  56 <p>The function starts to read data from the file at the position pointed by the read/write pointer. The read/write pointer advances as number of bytes read. After the function succeeded, <tt class="arg">*br</tt> should be checked to detect end of the file. In case of <tt class="arg">*br</tt> &lt; <tt class="arg">btr</tt>, it means the read/write pointer reached end of the file during read operation.</p>
  57 </div>
  58
  59
  60 <div class="para comp">
  61 <h4>QuickInfo</h4>
  62 <p>Always available.</p>
  63 </div>
  64
  65
  66 <div class="para ref">
  67 <h4>See Also</h4>
  68 <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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