89 lines
3.2 KiB
HTML
89 lines
3.2 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
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<html lang="en">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<meta http-equiv="Content-Style-Type" content="text/css">
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<link rel="up" title="FatFs" href="../00index_e.html">
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<link rel="alternate" hreflang="ja" title="Japanese" href="../ja/sync.html">
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<link rel="stylesheet" href="../css_e.css" type="text/css" media="screen" title="ELM Default">
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<title>FatFs - f_sync</title>
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</head>
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<body>
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<div class="para func">
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<h2>f_sync</h2>
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<p>The f_sync function flushes the cached information of a writing file.</p>
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<pre>
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FRESULT f_sync (
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FIL* <span class="arg">fp</span> <span class="c">/* [IN] File object */</span>
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);
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</pre>
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</div>
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<div class="para arg">
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<h4>Parameter</h4>
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<dl class="par">
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<dt>fp</dt>
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<dd>Pointer to the open file object to be flushed.</dd>
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</dl>
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</div>
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<div class="para ret">
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<h4>Return Values</h4>
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<p>
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<a href="rc.html#ok">FR_OK</a>,
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<a href="rc.html#de">FR_DISK_ERR</a>,
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<a href="rc.html#ie">FR_INT_ERR</a>,
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<a href="rc.html#io">FR_INVALID_OBJECT</a>,
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<a href="rc.html#tm">FR_TIMEOUT</a>
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</p>
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</div>
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<div class="para desc">
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<h4>Description</h4>
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<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>
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<pre>
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Case 1. Normal write sequence
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Time --> ↓Normal shutdown
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OwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwC <Power off>
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Case 2. Without using f_sync()
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Time --> ↓System crush
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O<span class="e">wwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwww</span>
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|<--------------- All data written will be lost ------------------>|
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Case 3. Using f_sync()
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Time --> ↓System crush
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OwwwwwwwwSwwwwwwwwSwwwwwwwwSwwwwwwwwSwwwwwwwwSwwwwwwwwSwwwwwwwwS<span class="e">wwwww</span>
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Data after last f_sync will be lost |<->|
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O - f_open()
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C - f_close()
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w - f_write()
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S - f_sync()
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</pre>
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<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>
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</div>
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<div class="para comp">
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<h4>QuickInfo</h4>
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<p>Available when <tt><a href="config.html#fs_readonly">FF_FS_READONLY</a> == 0</tt>.</p>
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</div>
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<div class="para ref">
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<h4>See Also</h4>
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<p><tt><a href="close.html">f_close</a></tt>, <a href="appnote.html#critical">Critical section</a></p>
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</div>
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<p class="foot"><a href="../00index_e.html">Return</a></p>
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</body>
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</html>
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