1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> 2<html lang="en"> 3<head> 4<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> 5<meta http-equiv="Content-Style-Type" content="text/css"> 6<link rel="stylesheet" href="../css_e.css" type="text/css" media="screen" title="ELM Default"> 7<title>FatFs - f_sync</title> 8</head> 9 10<body> 11 12<div class="para func"> 13<h2>f_sync</h2> 14<p>The f_sync function flushes the cached information of a writing file.</p> 15<pre> 16FRESULT f_sync ( 17 FIL* <span class="arg">fp</span> <span class="c">/* [IN] File object */</span> 18); 19</pre> 20</div> 21 22<div class="para arg"> 23<h4>Parameter</h4> 24<dl class="par"> 25<dt>fp</dt> 26<dd>Pointer to the open file object to be flushed.</dd> 27</dl> 28</div> 29 30 31<div class="para ret"> 32<h4>Return Values</h4> 33<p> 34<a href="rc.html#ok">FR_OK</a>, 35<a href="rc.html#de">FR_DISK_ERR</a>, 36<a href="rc.html#ie">FR_INT_ERR</a>, 37<a href="rc.html#io">FR_INVALID_OBJECT</a>, 38<a href="rc.html#tm">FR_TIMEOUT</a> 39</p> 40</div> 41 42 43<div class="para desc"> 44<h4>Description</h4> 45<p>The <tt>f_sync</tt> function performs the same process as <tt>f_close</tt> function but the file is left opened and can continue read/write/seek operations to the file. This is suitable for the applications that open files for a long time in write mode, such as data logger. Performing <tt>f_sync</tt> function in certain interval can minimize the risk of data loss due to a sudden blackout, wrong media removal or unrecoverable disk error. For more information, refer to <a href="appnote.html#critical">application note</a>.</p> 46<pre> 47Case 1. Normal write sequence 48 49 Time --> ↓Normal shutdown 50OwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwC <Power off> 51 52 53Case 2. Without using f_sync() 54 55 Time --> ↓System crush 56O<span class="e">wwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwww</span> 57 |<--------------- All data written will be lost ------------------>| 58 59 60Case 3. Using f_sync() 61 Time --> ↓System crush 62OwwwwwwwwSwwwwwwwwSwwwwwwwwSwwwwwwwwSwwwwwwwwSwwwwwwwwSwwwwwwwwS<span class="e">wwwww</span> 63 Data after last f_sync will be lost |<->| 64O - f_open() 65C - f_close() 66w - f_write() 67S - f_sync() 68</pre> 69<p>However there is no sense in <tt>f_sync</tt> function jsut before <tt>f_close</tt> function, because the <tt>f_close</tt> performs <tt>f_sync</tt> in it. Actually, the differnce between these functions is that the file object is invalidated or not.</p> 70</div> 71 72 73<div class="para comp"> 74<h4>QuickInfo</h4> 75<p>Available when <tt><a href="config.html#fs_readonly">FF_FS_READONLY</a> == 0</tt>.</p> 76</div> 77 78 79<div class="para ref"> 80<h4>See Also</h4> 81<p><tt><a href="close.html">f_close</a></tt>, <a href="appnote.html#critical">Critical section</a></p> 82</div> 83 84 85<p class="foot"><a href="../00index_e.html">Return</a></p> 86</body> 87</html> 88