fatfs/doc/en/open.html

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   9 <title>FatFs - f_open</title>
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  11
  12 <body>
  13
  14 <div class="para func">
  15 <h2>f_open</h2>
  16 <p>The f_open function creates a <em>file object</em> to be used to access the file.</p>
  17 <pre>
  18 FRESULT f_open (
  19   FIL* <span class="arg">fp</span>,           <span class="c">/* [OUT] Pointer to the file object structure */</span>
  20   const TCHAR* <span class="arg">path</span>, <span class="c">/* [IN] File name */</span>
  21   BYTE <span class="arg">mode</span>          <span class="c">/* [IN] Mode flags */</span>
  22 );
  23 </pre>
  24 </div>
  25
  26 <div class="para arg">
  27 <h4>Parameters</h4>
  28 <dl class="par">
  29 <dt>fp</dt>
  30 <dd>Pointer to the blank file object structure.</dd>
  31 <dt>path</dt>
  32 <dd>Pointer to the null-terminated string that specifies the <a href="filename.html">file name</a> to open or create.</dd>
  33 <dt>mode</dt>
  34 <dd>Mode flags that specifies the type of access and open method for the file. It is specified by a combination of following flags.<br>
  35 <table class="lst">
  36 <tr><th>Value</th><th>Meaning</th></tr>
  37 <tr><td>FA_READ</td><td>Specifies read access to the object. Data can be read from the file.</tr>
  38 <tr><td>FA_WRITE</td><td>Specifies write access to the object. Data can be written to the file. Combine with <tt>FA_READ</tt> for read-write access.</td></tr>
  39 <tr><td>FA_OPEN_EXISTING</td><td>Opens the file. The function fails if the file is not existing. (Default)</td></tr>
  40 <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>
  41 <tr><td>FA_CREATE_ALWAYS</td><td>Creates a new file. If the file is existing, it will be truncated and overwritten.</td></tr>
  42 <tr><td>FA_OPEN_ALWAYS</td><td>Opens the file if it is existing. If not, a new file will be created.</td></tr>
  43 <tr><td>FA_OPEN_APPEND</td><td>Same as <tt>FA_OPEN_ALWAYS</tt> except read/write pointer is set end of the file.</td></tr>
  44 </table>
  45 </dd>
  46 </dl>
  47 </div>
  48
  49
  50 <div class="para ret">
  51 <h4>Return Values</h4>
  52 <p>
  53 <a href="rc.html#ok">FR_OK</a>,
  54 <a href="rc.html#de">FR_DISK_ERR</a>,
  55 <a href="rc.html#ie">FR_INT_ERR</a>,
  56 <a href="rc.html#nr">FR_NOT_READY</a>,
  57 <a href="rc.html#ok">FR_NO_FILE</a>,
  58 <a href="rc.html#np">FR_NO_PATH</a>,
  59 <a href="rc.html#in">FR_INVALID_NAME</a>,
  60 <a href="rc.html#de">FR_DENIED</a>,
  61 <a href="rc.html#ex">FR_EXIST</a>,
  62 <a href="rc.html#io">FR_INVALID_OBJECT</a>,
  63 <a href="rc.html#wp">FR_WRITE_PROTECTED</a>,
  64 <a href="rc.html#id">FR_INVALID_DRIVE</a>,
  65 <a href="rc.html#ne">FR_NOT_ENABLED</a>,
  66 <a href="rc.html#ns">FR_NO_FILESYSTEM</a>,
  67 <a href="rc.html#tm">FR_TIMEOUT</a>,
  68 <a href="rc.html#lo">FR_LOCKED</a>,
  69 <a href="rc.html#nc">FR_NOT_ENOUGH_CORE</a>,
  70 <a href="rc.html#tf">FR_TOO_MANY_OPEN_FILES</a>
  71 </p>
  72 </div>
  73
  74
  75 <div class="para desc">
  76 <h4>Description</h4>
  77 <p>Before using any file function, a work area (file system object) needs to be registered to the logical drive with <a href="mount.html"><tt>f_mount</tt></a> function. All API functions except for <tt>f_mkfs/f_fdisk</tt> function get ready to work after this procedure.</p>
  78 <p>After <tt>f_open</tt> function succeeded, the file object is valid. The file object is used for subsequent operations to the file to identify the file. Open file must be closed prior to power down, media removal or re-mount, or the file can be collapsed. To close an open file, use <a href="close.html"><tt>f_close</tt></a> function.</p>
  79 <p>If duplicated file open is needed, read <a href="appnote.html#dup">here</a> carefully. However duplicated open of a file with any write mode flag is always prohibited.</p>
  80 </div>
  81
  82
  83 <div class="para comp">
  84 <h4>QuickInfo</h4>
  85 <p>Always available. Only <tt>FA_READ</tt> and <tt>FA_OPEN_EXISTING</tt> are supported when <tt>_FS_READONLY == 1</tt>.</p>
  86 </div>
  87
  88
  89 <div class="para use">
  90 <h4>Example</h4>
  91 <pre>
  92 <span class="c">/* Read a text file and display it */</span>
  93
  94 FATFS FatFs;   <span class="c">/* Work area (file system object) for logical drive */</span>
  95
  96 int main (void)
  97 {
  98     FIL fil;       <span class="c">/* File object */</span>
  99     char line[82]; <span class="c">/* Line buffer */</span>
 100     FRESULT fr;    <span class="c">/* FatFs return code */</span>
 101
 102
 103     <span class="c">/* Register work area to the default drive */</span>
 104     f_mount(&amp;FatFs, "", 0);
 105
 106     <span class="c">/* Open a text file */</span>
 107     fr = f_open(&amp;fil, "message.txt", FA_READ);
 108     if (fr) return (int)fr;
 109
 110     <span class="c">/* Read all lines and display it */</span>
 111     while (f_gets(line, sizeof line, &amp;fil))
 112         printf(line);
 113
 114     <span class="c">/* Close the file */</span>
 115     f_close(&amp;fil);
 116
 117     return 0;
 118 }
 119 </pre>
 120 <pre>
 121 <span class="c">/* Copy a file "file.bin" on the drive 1 to drive 0 */</span>
 122
 123 int main (void)
 124 {
 125     FATFS fs[2];         <span class="c">/* Work area (file system object) for logical drives */</span>
 126     FIL fsrc, fdst;      <span class="c">/* File objects */</span>
 127     BYTE buffer[4096];   <span class="c">/* File copy buffer */</span>
 128     FRESULT fr;          <span class="c">/* FatFs function common result code */</span>
 129     UINT br, bw;         <span class="c">/* File read/write count */</span>
 130
 131
 132     <span class="c">/* Register work area for each logical drive */</span>
 133     f_mount(&amp;fs[0], "0:", 0);
 134     f_mount(&amp;fs[1], "1:", 0);
 135
 136     <span class="c">/* Open source file on the drive 1 */</span>
 137     fr = f_open(&amp;fsrc, "1:file.bin", FA_READ);
 138     if (fr) return (int)fr;
 139
 140     <span class="c">/* Create destination file on the drive 0 */</span>
 141     fr = f_open(&amp;fdst, "0:file.bin", FA_WRITE | FA_CREATE_ALWAYS);
 142     if (fr) return (int)fr;
 143
 144     <span class="c">/* Copy source to destination */</span>
 145     for (;;) {
 146         fr = f_read(&amp;fsrc, buffer, sizeof buffer, &amp;br);  <span class="c">/* Read a chunk of source file */</span>
 147         if (fr || br == 0) break; <span class="c">/* error or eof */</span>
 148         fr = f_write(&amp;fdst, buffer, br, &amp;bw);            <span class="c">/* Write it to the destination file */</span>
 149         if (fr || bw &lt; br) break; <span class="c">/* error or disk full */</span>
 150     }
 151
 152     <span class="c">/* Close open files */</span>
 153     f_close(&amp;fsrc);
 154     f_close(&amp;fdst);
 155
 156     <span class="c">/* Unregister work area prior to discard it */</span>
 157     f_mount(NULL, "0:", 0);
 158     f_mount(NULL, "1:", 0);
 159
 160     return (int)fr;
 161 }
 162 </pre>
 163 </div>
 164
 165
 166 <div class="para ref">
 167 <h4>See Also</h4>
 168 <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>
 169 </div>
 170
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