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<title>FatFs - f_open</title>
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<body>

<div class="para func">
<h2>f_open</h2>
<p>The f_open function creates a <em>file object</em> to be used to access the file.</p>
<pre>
FRESULT f_open (
  FIL* <em>FileObject</em>,       <span class="c">/* Pointer to the blank file object structure */</span>
  const TCHAR* <em>FileName</em>, <span class="c">/* Pointer to the file neme */</span>
  BYTE <em>ModeFlags</em>         <span class="c">/* Mode flags */</span>
);
</pre>
</div>

<div class="para arg">
<h4>Parameters</h4>
<dl class="par">
<dt>FileObject</dt>
<dd>Pointer to the file object structure to be created.</dd>
<dt>FileName</dt>
<dd>Pointer to a null-terminated string that specifies the <a href="filename.html">file name</a> to create or open.</dd>
<dt>ModeFlags</dt>
<dd>Specifies the type of access and open method for the file. It is specified by a combination of following flags.<br>
<table class="lst">
<tr><th>Value</th><th>Description</th></tr>
<tr><td>FA_READ</td><td>Specifies read access to the object. Data can be read from the file.<br>Combine with <tt>FA_WRITE</tt> for read-write access.</td></tr>
<tr><td>FA_WRITE</td><td>Specifies write access to the object. Data can be written to the file.<br>Combine with <tt>FA_READ</tt> for read-write access.</td></tr>
<tr><td>FA_OPEN_EXISTING</td><td>Opens the file. The function fails if the file is not existing. (Default)</td></tr>
<tr><td>FA_OPEN_ALWAYS</td><td>Opens the file if it is existing. If not, a new file is created.<br>
To append data to the file, use <a href="lseek.html">f_lseek</a> function after file open in this method.</td></tr>
<tr><td>FA_CREATE_NEW</td><td>Creates a new file. The function fails with <tt>FR_EXIST</tt> if the file is existing.</td></tr>
<tr><td>FA_CREATE_ALWAYS</td><td>Creates a new file. If the file is existing, it is truncated and overwritten.</td></tr>
</table>
</dd>
</dl>
</div>


<div class="para ret">
<h4>Return Values</h4>
<p>
<a href="rc.html#ok">FR_OK</a>,
<a href="rc.html#de">FR_DISK_ERR</a>,
<a href="rc.html#ie">FR_INT_ERR</a>,
<a href="rc.html#nr">FR_NOT_READY</a>,
<a href="rc.html#ok">FR_NO_FILE</a>,
<a href="rc.html#np">FR_NO_PATH</a>,
<a href="rc.html#in">FR_INVALID_NAME</a>,
<a href="rc.html#de">FR_DENIED</a>,
<a href="rc.html#ex">FR_EXIST</a>,
<a href="rc.html#wp">FR_WRITE_PROTECTED</a>,
<a href="rc.html#id">FR_INVALID_DRIVE</a>,
<a href="rc.html#ne">FR_NOT_ENABLED</a>,
<a href="rc.html#ns">FR_NO_FILESYSTEM</a>,
<a href="rc.html#tm">FR_TIMEOUT</a>,
<a href="rc.html#lo">FR_LOCKED</a>,
<a href="rc.html#nc">FR_NOT_ENOUGH_CORE</a>,
<a href="rc.html#tf">FR_TOO_MANY_OPEN_FILES</a>
</p>
</div>


<div class="para desc">
<h4>Description</h4>
<p>After f_open function succeeded, the file object is valid. The file object is used for subsequent read/write functions to identify the file. When close an open file object, use <a href="close.html">f_close</a> function. If the modified file is not closed, the file data can be collapsed.</p>
<p>If duplicated file open is needed, read <a href="appnote.html#dup">here</a> carefully.</p>
<p>Before using any file function, a work area (file system object) must be registered to the logical drive with <a href="mount.html">f_mount</a> function. All API functions except for <a href="fdisk.html">f_fdisk</a> function can work after this procedure.</p>
</div>


<div class="para comp">
<h4>QuickInfo</h4>
<p>Always available. The mode flags, <tt>FA_WRITE, FA_CREATE_ALWAYS, FA_CREATE_NEW and FA_OPEN_ALWAYS</tt>, are not available when <tt>_FS_READONLY == 1</tt>.</p>
</div>


<div class="para use">
<h4>Example (File Copy)</h4>
<pre>
void main (void)
{
    FATFS fs[2];         <span class="c">/* Work area (file system object) for logical drives */</span>
    FIL fsrc, fdst;      <span class="c">/* file objects */</span>
    BYTE buffer[4096];   <span class="c">/* file copy buffer */</span>
    FRESULT res;         <span class="c">/* FatFs function common result code */</span>
    UINT br, bw;         <span class="c">/* File read/write count */</span>


    <span class="c">/* Register work area for each volume (Always succeeds regardless of disk status) */</span>
    f_mount(0, &amp;fs[0]);
    f_mount(1, &amp;fs[1]);

    <span class="c">/* Open source file on the drive 1 */</span>
    res = f_open(&amp;fsrc, "1:srcfile.dat", FA_OPEN_EXISTING | FA_READ);
    if (res) die(res);

    <span class="c">/* Create destination file on the drive 0 */</span>
    res = f_open(&amp;fdst, "0:dstfile.dat", FA_CREATE_ALWAYS | FA_WRITE);
    if (res) die(res);

    <span class="c">/* Copy source to destination */</span>
    for (;;) {
        res = f_read(&amp;fsrc, buffer, sizeof buffer, &amp;br);     <span class="c">/* Read a chunk of src file */</span>
        if (res || br == 0) break; <span class="c">/* error or eof */</span>
        res = f_write(&amp;fdst, buffer, br, &amp;bw);               <span class="c">/* Write it to the dst file */</span>
        if (res || bw &lt; br) break; <span class="c">/* error or disk full */</span>
    }

    <span class="c">/* Close open files */</span>
    f_close(&amp;fsrc);
    f_close(&amp;fdst);

    <span class="c">/* Unregister work area prior to discard it */</span>
    f_mount(0, NULL);
    f_mount(1, NULL);
}
</pre>
</div>


<div class="para ref">
<h4>See Also</h4>
<p><tt><a href="read.html">f_read</a>, <a href="write.html">f_write</a>, <a href="close.html">f_close</a>, <a href="sfile.html">FIL</a>, <a href="sfatfs.html">FATFS</a></tt></p>
</div>

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