fatfs/documents/doc/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 opens a 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>Flags</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 the read/write pointer is set end of the file.</td></tr>
  44 </table>
  45 Mode flags of POSIX fopen() corresponds to FatFs mode flags as follows:<br>
  46 <table class="lst2">
  47 <tr><th>POSIX</th><th>FatFs</th></tr>
  48 <tr><td>"r"</td><td>FA_READ</td></tr>
  49 <tr><td>"r+"</td><td>FA_READ | FA_WRITE</td></tr>
  50 <tr><td>"w"</td><td>FA_CREATE_ALWAYS | FA_WRITE</td></tr>
  51 <tr><td>"w+"</td><td>FA_CREATE_ALWAYS | FA_WRITE | FA_READ</td></tr>
  52 <tr><td>"a"</td><td>FA_OPEN_APPEND | FA_WRITE</td></tr>
  53 <tr><td>"a+"</td><td>FA_OPEN_APPEND | FA_WRITE | FA_READ</td></tr>
  54 <tr><td>"wx"</td><td>FA_CREATE_NEW | FA_WRITE</td></tr>
  55 <tr><td>"w+x"</td><td>FA_CREATE_NEW | FA_WRITE | FA_READ</td></tr>
  56 </table>
  57 </dd>
  58 </dl>
  59 </div>
  60
  61
  62 <div class="para ret">
  63 <h4>Return Values</h4>
  64 <p>
  65 <a href="rc.html#ok">FR_OK</a>,
  66 <a href="rc.html#de">FR_DISK_ERR</a>,
  67 <a href="rc.html#ie">FR_INT_ERR</a>,
  68 <a href="rc.html#nr">FR_NOT_READY</a>,
  69 <a href="rc.html#nf">FR_NO_FILE</a>,
  70 <a href="rc.html#np">FR_NO_PATH</a>,
  71 <a href="rc.html#in">FR_INVALID_NAME</a>,
  72 <a href="rc.html#dn">FR_DENIED</a>,
  73 <a href="rc.html#ex">FR_EXIST</a>,
  74 <a href="rc.html#io">FR_INVALID_OBJECT</a>,
  75 <a href="rc.html#wp">FR_WRITE_PROTECTED</a>,
  76 <a href="rc.html#id">FR_INVALID_DRIVE</a>,
  77 <a href="rc.html#ne">FR_NOT_ENABLED</a>,
  78 <a href="rc.html#ns">FR_NO_FILESYSTEM</a>,
  79 <a href="rc.html#tm">FR_TIMEOUT</a>,
  80 <a href="rc.html#lo">FR_LOCKED</a>,
  81 <a href="rc.html#nc">FR_NOT_ENOUGH_CORE</a>,
  82 <a href="rc.html#tf">FR_TOO_MANY_OPEN_FILES</a>
  83 </p>
  84 </div>
  85
  86
  87 <div class="para desc">
  88 <h4>Description</h4>
  89 <p>The <tt>f_open</tt> function opens a file and creates a <em>file object</em>. The file object is used for subsequent read/write operations to the file to identify the file. Open file should be closed with <a href="close.html"><tt>f_close</tt></a> function after the session of the file access. If any change to the file is made and not closed prior to power down, media removal or re-mount, or the file can be collapsed.</p>
  90 <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>
  91 </div>
  92
  93
  94 <div class="para comp">
  95 <h4>QuickInfo</h4>
  96 <p>Always available. Only <tt>FA_READ</tt> and <tt>FA_OPEN_EXISTING</tt> are available for the mode flags when <tt><a href="config.html#fs_readonly">FF_FS_READONLY</a> == 1</tt>.</p>
  97 </div>
  98
  99
 100 <div class="para use">
 101 <h4>Example</h4>
 102 <pre>
 103 <span class="c">/* Read a text file and display it */</span>
 104
 105 FATFS FatFs;   <span class="c">/* Work area (filesystem object) for logical drive */</span>
 106
 107 int main (void)
 108 {
 109     FIL fil;        <span class="c">/* File object */</span>
 110     char line[100]; <span class="c">/* Line buffer */</span>
 111     FRESULT fr;     <span class="c">/* FatFs return code */</span>
 112
 113
 114     <span class="c">/* Register work area to the default drive */</span>
 115     f_mount(&amp;FatFs, "", 0);
 116
 117     <span class="c">/* Open a text file */</span>
 118     fr = <em>f_open</em>(&amp;fil, "message.txt", FA_READ);
 119     if (fr) return (int)fr;
 120
 121     <span class="c">/* Read all lines and display it */</span>
 122     while (f_gets(line, sizeof line, &amp;fil)) {
 123         printf(line);
 124     }
 125
 126     <span class="c">/* Close the file */</span>
 127     f_close(&amp;fil);
 128
 129     return 0;
 130 }
 131 </pre>
 132 <pre>
 133 <span class="c">/* Copy a file "file.bin" on the drive 1 to drive 0 */</span>
 134
 135 int main (void)
 136 {
 137     FATFS fs[2];         <span class="c">/* Work area (filesystem object) for logical drives */</span>
 138     FIL fsrc, fdst;      <span class="c">/* File objects */</span>
 139     BYTE buffer[4096];   <span class="c">/* File copy buffer */</span>
 140     FRESULT fr;          <span class="c">/* FatFs function common result code */</span>
 141     UINT br, bw;         <span class="c">/* File read/write count */</span>
 142
 143
 144     <span class="c">/* Register work area for each logical drive */</span>
 145     f_mount(&amp;fs[0], "0:", 0);
 146     f_mount(&amp;fs[1], "1:", 0);
 147
 148     <span class="c">/* Open source file on the drive 1 */</span>
 149     fr = <em>f_open</em>(&amp;fsrc, "1:file.bin", FA_READ);
 150     if (fr) return (int)fr;
 151
 152     <span class="c">/* Create destination file on the drive 0 */</span>
 153     fr = <em>f_open</em>(&amp;fdst, "0:file.bin", FA_WRITE | FA_CREATE_ALWAYS);
 154     if (fr) return (int)fr;
 155
 156     <span class="c">/* Copy source to destination */</span>
 157     for (;;) {
 158         fr = f_read(&amp;fsrc, buffer, sizeof buffer, &amp;br);  <span class="c">/* Read a chunk of source file */</span>
 159         if (fr || br == 0) break; <span class="c">/* error or eof */</span>
 160         fr = f_write(&amp;fdst, buffer, br, &amp;bw);            <span class="c">/* Write it to the destination file */</span>
 161         if (fr || bw &lt; br) break; <span class="c">/* error or disk full */</span>
 162     }
 163
 164     <span class="c">/* Close open files */</span>
 165     f_close(&amp;fsrc);
 166     f_close(&amp;fdst);
 167
 168     <span class="c">/* Unregister work area prior to discard it */</span>
 169     f_mount(NULL, "0:", 0);
 170     f_mount(NULL, "1:", 0);
 171
 172     return (int)fr;
 173 }
 174 </pre>
 175 </div>
 176
 177
 178 <div class="para ref">
 179 <h4>See Also</h4>
 180 <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>
 181 </div>
 182
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