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_printf</title> 8</head> 9 10<body> 11 12<div class="para func"> 13<h2>f_printf</h2> 14<p>The f_printf function writes formatted string to the file.</p> 15<pre> 16int f_printf ( 17 FIL* <span class="arg">fp</span>, <span class="c">/* [IN] File object */</span> 18 const TCHAR* <span class="arg">fmt</span>, <span class="c">/* [IN] Format stirng */</span> 19 ... 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 open file object structure.</dd> 29<dt>fmt</dt> 30<dd>Pointer to the null <tt>'\0'</tt> terminated format string. The terminator character will not be output.</dd> 31<dt>...</dt> 32<dd>Optional arguments...</dd> 33 34</dl> 35</div> 36 37 38<div class="para ret"> 39<h4>Return Values</h4> 40<p>When the string was written successfuly, it returns number of character encoding units written to the file. When the function failed due to disk full or an error, a negative value will be returned.</p> 41</div> 42 43 44<div class="para desc"> 45<h4>Description</h4> 46<p>The format control directive is a sub-set of standard library shown as follows:</p> 47<pre> 48 %[flag][width][precision][size]type 49</pre> 50<dl> 51<dt>flag</dt><dd>Padding option. A <tt>-</tt> specifies left-aligned. A <tt>0</tt> specifies zero padded. The default setting is in right-aligned and space padded.</dd> 52<dt>width</dt><dd>Minimum width of the field, <tt>1-99</tt> or <tt>*</tt>. If the width of generated string is less than the minimum width, rest field is padded with spaces or zeros. An <tt>*</tt> specifies the value comes from an argument in int type. The default setting is zero.</dd> 53<dt>precision</dt><dd>Specifies number of fractional digits or maximum width of string, <tt>.0-.99</tt> or <tt>.*</tt>. If the number is omitted, it is same as <tt>.0</tt>. Default setting is 6 for number and no limit for string.</dd> 54<dt>size</dt><dd>Specifies size of integer argument, <tt>l</tt>(long) and <tt>ll</tt>(long long). If <tt>sizeof (long) == sizeof (int)</tt> is true (this is typical of 32-bit systems), prefix <tt>l</tt> can be omitted for long integer argument. The default size is int for integer argument and floating point argument is always assumed double as the default argument promotion.</dd> 55<dt>type</dt><dd>Specifies type of the output format and the argument as shown below. The length of generated string is in assumtion of int is 32-bit. 56<table class="lst1"> 57<tr><th>Type</th><th>Format</th><th>Argument</th><th>Length</th></tr> 58<tr><td><tt>c</tt></td><td>Character</td><td rowspan="6"><tt>int</tt>,<br><tt>long</tt>,<br><tt>long long</tt></td><td>1 character.</td></tr> 59<tr><td><tt>d</tt></td><td>Signed decimal</td><td>1 to 11 (20 for ll) characters.</td></tr> 60<tr><td><tt>u</tt></td><td>Unsigned decimal</td><td>1 to 10 (20 for ll) characters.</td></tr> 61<tr><td><tt>o</tt></td><td>Unsigned octal</td><td>1 to 11 (22 for ll) characters.</td></tr> 62<tr><td><tt>x X</tt></td><td>Unsigned hexdecimal</td><td>1 to 8 (16 for ll) characters.</td></tr> 63<tr><td><tt>b</tt></td><td>Unsigned binary</td><td>1 to 32 characters. Limited to lower 32 digits when ll is specified.</td></tr> 64<tr><td><tt>s</tt></td><td>String</td><td><tt>TCHAR*</tt></td><td>As input string. A null pointer generates a zero-length string.</td></tr> 65<tr><td><tt>f</tt></td><td>Floating point<br>(decimal)</td><td rowspan="2"><tt>double</tt></td><td>1 to 31 characters. If the number of characters exceeds 31, it writes <tt>"±OV"</tt>. Not a number and infinite value write <tt>"NaN"</tt> and <tt>"±INF"</tt> respectively.</td></tr> 66<tr><td><tt>e E</tt></td><td>Floating point<br>(e notation)</td><td>4 to 31 characters. If the number of characters exceeds 31 or exponent exceeds +99, it writes <tt>"±OV"</tt>.</td></tr> 67</table> 68</dd> 69</dl> 70<p>When FatFs is configured for Unicode API (<tt><a href="config.html#lfn_unicode">FF_LFN_UNICODE</a> >= 1</tt>), character encoding on the string fuctions, <tt>f_putc</tt>, <tt>f_puts</tt>, <tt>f_printf</tt> and <tt>f_gets</tt> function, is also switched to Unicode. The Unicode characters in multiple encoding unit, such as surrogate pair and multi-byte sequence, should not be divided into two function calls, or the character will be lost. The character encoding <em>on the file</em> to be written via this function is selected by <tt><a href="config.html#strf_encode">FF_STRF_ENCODE</a></tt>. If the character encoding differs between file data and API, it is converted in this function. Input characters with wrong encoding for output will be lost.</p> 71<p>If <tt>sprintf</tt> is used in the project and code conversion is not needed, <tt>f_write</tt> with <tt>sprintf</tt> will be efficient in code size and performance rather than <tt>f_printf</tt>.</p> 72</div> 73 74 75<div class="para comp"> 76<h4>QuickInfo</h4> 77<p>This is a wrapper function of <a href="write.html"><tt>f_write</tt></a> function. Available when <tt><a href="config.html#fs_readonly">FF_FS_READONLY</a> == 0</tt> and <tt><a href="config.html#use_strfunc">FF_USE_STRFUNC</a> >= 1</tt>. When <tt>FF_USE_STRFUNC == 2</tt>, <tt>'\n'</tt>s in the generated string are written as <tt>'\r'+'\n'</tt> each.</p> 78</div> 79 80 81<div class="para use"> 82<h4>Example</h4> 83<pre> 84 <em>f_printf</em>(fp, "%d", 1234); <span class="c">/* "1234" */</span> 85 <em>f_printf</em>(fp, "%6d,%3d%%", -200, 5); <span class="c">/* " -200, 5%" */</span> 86 <em>f_printf</em>(fp, "%-6u", 100); <span class="c">/* "100 " */</span> 87 <em>f_printf</em>(fp, "%ld", 12345678); <span class="c">/* "12345678" */</span> 88 <em>f_printf</em>(fp, "%llu", 0x100000000); <span class="c">/* "4294967296" (<a href="config.html#print_lli">FF_PRINT_LLI</a>) */</span> 89 <em>f_printf</em>(fp, "%lld", -1LL); <span class="c">/* "-1" (FF_PRINT_LLI) */</span> 90 <em>f_printf</em>(fp, "%04x", 0xA3); <span class="c">/* "00a3" */</span> 91 <em>f_printf</em>(fp, "%08lX", 0x123ABC); <span class="c">/* "00123ABC" */</span> 92 <em>f_printf</em>(fp, "%016b", 0x550F); <span class="c">/* "0101010100001111" */</span> 93 <em>f_printf</em>(fp, "%*d", 6, 100); <span class="c">/* " 100" */</span> 94 <em>f_printf</em>(fp, "%s", "abcdefg"); <span class="c">/* "abcdefg" */</span> 95 <em>f_printf</em>(fp, "%5s", "abc"); <span class="c">/* " abc" */</span> 96 <em>f_printf</em>(fp, "%-5s", "abc"); <span class="c">/* "abc " */</span> 97 <em>f_printf</em>(fp, "%.5s", "abcdefg"); <span class="c">/* "abcde" */</span> 98 <em>f_printf</em>(fp, "%-5.2s", "abcdefg"); <span class="c">/* "ab " */</span> 99 <em>f_printf</em>(fp, "%c", 'a'); <span class="c">/* "a" */</span> 100 <em>f_printf</em>(fp, "%12f", 10.0); <span class="c">/* " 10.000000" (<a href="config.html#print_fp">FF_PRINT_FLOAT</a>) */</span> 101 <em>f_printf</em>(fp, "%.4E", 123.45678); <span class="c">/* "1.2346E+02" (FF_PRINT_FLOAT) */</span> 102</pre> 103</div> 104 105 106<div class="para ref"> 107<h4>See Also</h4> 108<p><tt><a href="open.html">f_open</a>, <a href="putc.html">f_putc</a>, <a href="puts.html">f_puts</a>, <a href="gets.html">f_gets</a>, <a href="close.html">f_close</a>, <a href="sfile.html">FIL</a></tt></p> 109</div> 110 111 112<p class="foot"><a href="../00index_e.html">Return</a></p> 113</body> 114</html> 115