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="up" title="FatFs" href="../00index_e.html"> 7<link rel="alternate" hreflang="ja" title="Japanese" href="../ja/sync.html"> 8<link rel="stylesheet" href="../css_e.css" type="text/css" media="screen" title="ELM Default"> 9<title>FatFs - f_sync</title> 10</head> 11 12<body> 13 14<div class="para func"> 15<h2>f_sync</h2> 16<p>The f_sync function flushes the cached information of a writing file.</p> 17<pre> 18FRESULT f_sync ( 19 FIL* <span class="arg">fp</span> <span class="c">/* [IN] File object */</span> 20); 21</pre> 22</div> 23 24<div class="para arg"> 25<h4>Parameter</h4> 26<dl class="par"> 27<dt>fp</dt> 28<dd>Pointer to the open file object to be flushed.</dd> 29</dl> 30</div> 31 32 33<div class="para ret"> 34<h4>Return Values</h4> 35<p> 36<a href="rc.html#ok">FR_OK</a>, 37<a href="rc.html#de">FR_DISK_ERR</a>, 38<a href="rc.html#ie">FR_INT_ERR</a>, 39<a href="rc.html#io">FR_INVALID_OBJECT</a>, 40<a href="rc.html#tm">FR_TIMEOUT</a> 41</p> 42</div> 43 44 45<div class="para desc"> 46<h4>Description</h4> 47<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> 48<pre> 49Case 1. Normal write sequence 50 51 Time --> ↓Normal shutdown 52OwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwC <Power off> 53 54 55Case 2. Without using f_sync() 56 57 Time --> ↓System crush 58O<span class="e">wwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwww</span> 59 |<--------------- All data written will be lost ------------------>| 60 61 62Case 3. Using f_sync() 63 Time --> ↓System crush 64OwwwwwwwwSwwwwwwwwSwwwwwwwwSwwwwwwwwSwwwwwwwwSwwwwwwwwSwwwwwwwwS<span class="e">wwwww</span> 65 Data after last f_sync will be lost |<->| 66O - f_open() 67C - f_close() 68w - f_write() 69S - f_sync() 70</pre> 71<p>However there is no sense in <tt>f_sync</tt> function immediataly before <tt>f_close</tt> function because it performs <tt>f_sync</tt> function in it. In other words, the differnce between those functions is that the file object is invalidated or not.</p> 72</div> 73 74 75<div class="para comp"> 76<h4>QuickInfo</h4> 77<p>Available when <tt><a href="config.html#fs_readonly">FF_FS_READONLY</a> == 0</tt>.</p> 78</div> 79 80 81<div class="para ref"> 82<h4>See Also</h4> 83<p><tt><a href="close.html">f_close</a></tt>, <a href="appnote.html#critical">Critical section</a></p> 84</div> 85 86<p class="foot"><a href="../00index_e.html">Return</a></p> 87</body> 88</html> 89