fatfs/documents/doc/write.html

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   9 <title>FatFs - f_write</title>
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  13
  14 <div class="para func">
  15 <h2>f_write</h2>
  16 <p>The f_write writes data to a file.</p>
  17 <pre>
  18 FRESULT f_write (
  19   FIL* <span class="arg">fp</span>,          <span class="c">/* [IN] Pointer to the file object structure */</span>
  20   const void* <span class="arg">buff</span>, <span class="c">/* [IN] Pointer to the data to be written */</span>
  21   UINT <span class="arg">btw</span>,         <span class="c">/* [IN] Number of bytes to write */</span>
  22   UINT* <span class="arg">bw</span>          <span class="c">/* [OUT] Pointer to the variable to return number of bytes written */</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 structure.</dd>
  32 <dt>buff</dt>
  33 <dd>Pointer to the data to be written.</dd>
  34 <dt>btw</dt>
  35 <dd>Specifies number of bytes to write in range of <tt>UINT</tt> type.</dd>
  36 <dt>bw</dt>
  37 <dd>Pointer to the <tt>UINT</tt> variable to return the number of bytes written. This value is always valid after the function call regardless of the function return 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#dn">FR_DENIED</a>,
  49 <a href="rc.html#io">FR_INVALID_OBJECT</a>,
  50 <a href="rc.html#tm">FR_TIMEOUT</a>
  51 </p>
  52 </div>
  53
  54
  55 <div class="para desc">
  56 <h4>Description</h4>
  57 <p>The function starts to write data to the file at the position pointed by the read/write pointer. The read/write pointer advances as number of bytes written. After the function succeeded, <tt class="arg">*bw</tt> should be checked to detect the disk full. In case of <tt class="arg">*bw</tt> &lt; <tt class="arg">btw</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>
  58 </div>
  59
  60
  61 <div class="para comp">
  62 <h4>QuickInfo</h4>
  63 <p>Available when <tt><a href="config.html#fs_readonly">FF_FS_READONLY</a> == 0</tt>.</p>
  64 </div>
  65
  66
  67 <div class="para ref">
  68 <h4>See Also</h4>
  69 <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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