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="stylesheet" href="../css_e.css" type="text/css" media="screen" title="ELM Default"> 7<title>FatFs - f_open</title> 8</head> 9 10<body> 11 12<div class="para func"> 13<h2>f_open</h2> 14<p>The f_open function opens a file.</p> 15<pre> 16FRESULT f_open ( 17 FIL* <span class="arg">fp</span>, <span class="c">/* [OUT] Pointer to the file object structure */</span> 18 const TCHAR* <span class="arg">path</span>, <span class="c">/* [IN] File name */</span> 19 BYTE <span class="arg">mode</span> <span class="c">/* [IN] Mode flags */</span> 20); 21</pre> 22</div> 23 24<div class="para arg"> 25<h4>Parameters</h4> 26<dl class="par"> 27<dt>fp</dt> 28<dd>Pointer to the blank file object structure. If a null pointer is given, the function fails with <tt>FR_INVALID_OBJECT</tt>.</dd> 29<dt>path</dt> 30<dd>Pointer to the null-terminated string that specifies the <a href="filename.html">file name</a> to open or create. If a null pointer is given, the function fails with <tt>FR_INVALID_DRIVE</tt>.</dd> 31<dt>mode</dt> 32<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> 33<table class="lst"> 34<tr><th>Flags</th><th>Meaning</th></tr> 35<tr><td>FA_READ</td><td>Specifies read access to the file. Data can be read from the file.</tr> 36<tr><td>FA_WRITE</td><td>Specifies write access to the file. Data can be written to the file. Combine with <tt>FA_READ</tt> for read-write access.</td></tr> 37<tr><td>FA_OPEN_EXISTING</td><td>Opens the file. The function fails if the file is not existing. (Default)</td></tr> 38<tr><td>FA_CREATE_ALWAYS</td><td>Creates a new file. If the file is existing, the file is truncated and overwritten.</td></tr> 39<tr><td>FA_CREATE_NEW</td><td>Creates a new file. The function fails if the file is existing.</td></tr> 40<tr><td>FA_OPEN_ALWAYS</td><td>Opens the file. If it is not exist, a new file is created.</td></tr> 41<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> 42</table> 43Mode flags in POSIX fopen() function corresponds to FatFs mode flags as follows:<br> 44<table class="lst2"> 45<tr><th>POSIX</th><th>FatFs</th></tr> 46<tr><td>"r"</td><td>FA_READ</td></tr> 47<tr><td>"r+"</td><td>FA_READ | FA_WRITE</td></tr> 48<tr><td>"w"</td><td>FA_CREATE_ALWAYS | FA_WRITE</td></tr> 49<tr><td>"w+"</td><td>FA_CREATE_ALWAYS | FA_WRITE | FA_READ</td></tr> 50<tr><td>"a"</td><td>FA_OPEN_APPEND | FA_WRITE</td></tr> 51<tr><td>"a+"</td><td>FA_OPEN_APPEND | FA_WRITE | FA_READ</td></tr> 52<tr><td>"wx"</td><td>FA_CREATE_NEW | FA_WRITE</td></tr> 53<tr><td>"w+x"</td><td>FA_CREATE_NEW | FA_WRITE | FA_READ</td></tr> 54</table> 55</dd> 56</dl> 57</div> 58 59 60<div class="para ret"> 61<h4>Return Values</h4> 62<p> 63<a href="rc.html#ok">FR_OK</a>, 64<a href="rc.html#de">FR_DISK_ERR</a>, 65<a href="rc.html#ie">FR_INT_ERR</a>, 66<a href="rc.html#nr">FR_NOT_READY</a>, 67<a href="rc.html#nf">FR_NO_FILE</a>, 68<a href="rc.html#np">FR_NO_PATH</a>, 69<a href="rc.html#in">FR_INVALID_NAME</a>, 70<a href="rc.html#dn">FR_DENIED</a>, 71<a href="rc.html#ex">FR_EXIST</a>, 72<a href="rc.html#io">FR_INVALID_OBJECT</a>, 73<a href="rc.html#wp">FR_WRITE_PROTECTED</a>, 74<a href="rc.html#id">FR_INVALID_DRIVE</a>, 75<a href="rc.html#ne">FR_NOT_ENABLED</a>, 76<a href="rc.html#ns">FR_NO_FILESYSTEM</a>, 77<a href="rc.html#tm">FR_TIMEOUT</a>, 78<a href="rc.html#lo">FR_LOCKED</a>, 79<a href="rc.html#nc">FR_NOT_ENOUGH_CORE</a>, 80<a href="rc.html#tf">FR_TOO_MANY_OPEN_FILES</a> 81</p> 82</div> 83 84 85<div class="para desc"> 86<h4>Description</h4> 87<p>The <tt>f_open</tt> function opens a file and creates a <em>file object</em>. It is the identifier for subsequent read/write operations to the file. After the function succeeded, the file object is valid. If the function failed, the file object is set invalid.</p> 88<p>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 has been made and not closed prior to power off, media removal or re-mount, or the file can be collapsed.</p> 89<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> 90</div> 91 92 93<div class="para comp"> 94<h4>QuickInfo</h4> 95<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> 96</div> 97 98 99<div class="para use"> 100<h4>Example</h4> 101<pre> 102<span class="c">/* Read a text file and display it */</span> 103 104FATFS FatFs; <span class="c">/* Work area (filesystem object) for logical drive */</span> 105 106int main (void) 107{ 108 FIL fil; <span class="c">/* File object */</span> 109 char line[100]; <span class="c">/* Line buffer */</span> 110 FRESULT fr; <span class="c">/* FatFs return code */</span> 111 112 113 <span class="c">/* Give a work area to the default drive */</span> 114 <em>f_mount</em>(&FatFs, "", 0); 115 116 <span class="c">/* Open a text file */</span> 117 fr = <em>f_open</em>(&fil, "message.txt", FA_READ); 118 if (fr) return (int)fr; 119 120 <span class="c">/* Read every line and display it */</span> 121 while (<em>f_gets</em>(line, sizeof line, &fil)) { 122 printf(line); 123 } 124 125 <span class="c">/* Close the file */</span> 126 <em>f_close</em>(&fil); 127 128 return 0; 129} 130</pre> 131<pre> 132<span class="c">/* Copy a file "file.bin" on the drive 1 to drive 0 */</span> 133 134int main (void) 135{ 136 FATFS fs0, fs1; <span class="c">/* Work area (filesystem object) for logical drives */</span> 137 FIL fsrc, fdst; <span class="c">/* File objects */</span> 138 BYTE buffer[4096]; <span class="c">/* File copy buffer */</span> 139 FRESULT fr; <span class="c">/* FatFs function common result code */</span> 140 UINT br, bw; <span class="c">/* File read/write count */</span> 141 142 143 <span class="c">/* Give work areas to each logical drive */</span> 144 <em>f_mount</em>(&fs0, "0:", 0); 145 <em>f_mount</em>(&fs1, "1:", 0); 146 147 <span class="c">/* Open source file on the drive 1 */</span> 148 fr = <em>f_open</em>(&fsrc, "1:file.bin", FA_READ); 149 if (fr) return (int)fr; 150 151 <span class="c">/* Create destination file on the drive 0 */</span> 152 fr = <em>f_open</em>(&fdst, "0:file.bin", FA_WRITE | FA_CREATE_ALWAYS); 153 if (fr) return (int)fr; 154 155 <span class="c">/* Copy source to destination */</span> 156 for (;;) { 157 fr = <em>f_read</em>(&fsrc, buffer, sizeof buffer, &br); <span class="c">/* Read a chunk of data from the source file */</span> 158 if (br == 0) break; <span class="c">/* error or eof */</span> 159 fr = <em>f_write</em>(&fdst, buffer, br, &bw); <span class="c">/* Write it to the destination file */</span> 160 if (bw < br) break; <span class="c">/* error or disk full */</span> 161 } 162 163 <span class="c">/* Close open files */</span> 164 <em>f_close</em>(&fsrc); 165 <em>f_close</em>(&fdst); 166 167 <span class="c">/* Unregister work area prior to discard it */</span> 168 <em>f_unmount</em>("0:"); 169 <em>f_unmount</em>("1:"); 170 171 return (int)fr; 172} 173</pre> 174</div> 175 176 177<div class="para ref"> 178<h4>See Also</h4> 179<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> 180</div> 181 182 183<p class="foot"><a href="../00index_e.html">Return</a></p> 184</body> 185</html> 186