99 lines
5.5 KiB
HTML
99 lines
5.5 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
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<html lang="en">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<meta http-equiv="Content-Style-Type" content="text/css">
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<link rel="up" title="FatFs" href="../00index_e.html">
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<link rel="alternate" hreflang="ja" title="Japanese" href="../ja/printf.html">
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<link rel="stylesheet" href="../css_e.css" type="text/css" media="screen" title="ELM Default">
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<title>FatFs - f_printf</title>
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</head>
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<body>
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<div class="para func">
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<h2>f_printf</h2>
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<p>The f_printf function writes formatted string to the file.</p>
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<pre>
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int f_printf (
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FIL* <span class="arg">fp</span>, <span class="c">/* [IN] File object */</span>
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const TCHAR* <span class="arg">fmt</span>, <span class="c">/* [IN] Format stirng */</span>
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...
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);
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</pre>
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</div>
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<div class="para arg">
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<h4>Parameters</h4>
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<dl class="par">
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<dt>fp</dt>
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<dd>Pointer to the open file object structure.</dd>
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<dt>fmt</dt>
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<dd>Pointer to the null <tt>'\0'</tt> terminated format string. The terminator character will not be output.</dd>
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<dt>...</dt>
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<dd>Optional arguments...</dd>
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</dl>
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</div>
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<div class="para ret">
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<h4>Return Values</h4>
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<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 any error, an <tt>EOF (-1)</tt> will be returned.</p>
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</div>
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<div class="para desc">
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<h4>Description</h4>
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<p>The format control directive is a sub-set of standard library shown as follows:</p>
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<pre>
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%[flag][width][type]
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</pre>
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<dl>
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<dt>flag</dt><dd>Padding options. A <tt>-</tt> specifies left justified. A <tt>0</tt> specifies zero padded.</dd>
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<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 specified value, rest field is padded with white spaces or zeros. An <tt>*</tt> specifies the value comes from an argument in int type.</dd>
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<dt>type</dt><dd><tt>c s d u o x b</tt> and prefix <tt>l</tt> specify type of the argument, character, string, signed integer in decimal, unsigned integer in decimal, unsigned integer in octal, unsigned integer in hexdecimal and unsigned integer in binary respectively. If <tt>sizeof (long)</tt> is greater than <tt>sizeof (int)</tt> (this is typical of 8/16-bit systems), a prefix <tt>l</tt> needs to be explicitly specified for long integer argument. These characters except for <tt>x</tt> are case insensitive.</dd>
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</dl>
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<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>. The characters with wrong encoding or invalid for the output encoding will be lost.</p>
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</div>
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<div class="para comp">
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<h4>QuickInfo</h4>
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<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>
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</div>
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<div class="para use">
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<h4>Example</h4>
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<pre>
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<em>f_printf</em>(&fil, "%d", 1234); <span class="c">/* "1234" */</span>
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<em>f_printf</em>(&fil, "%6d,%3d%%", -200, 5); <span class="c">/* " -200, 5%" */</span>
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<em>f_printf</em>(&fil, "%ld", 12345L); <span class="c">/* "12345" */</span>
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<em>f_printf</em>(&fil, "%06d", 25); <span class="c">/* "000025" */</span>
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<em>f_printf</em>(&fil, "%06d", -25); <span class="c">/* "000-25" */</span>
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<em>f_printf</em>(&fil, "%*d", 5, 100); <span class="c">/* " 100" */</span>
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<em>f_printf</em>(&fil, "%-6d", 25); <span class="c">/* "25 " */</span>
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<em>f_printf</em>(&fil, "%u", -1); <span class="c">/* "65535" or "4294967295" */</span>
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<em>f_printf</em>(&fil, "%04x", 0xAB3); <span class="c">/* "0ab3" */</span>
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<em>f_printf</em>(&fil, "%08lX", 0x123ABCL); <span class="c">/* "00123ABC" */</span>
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<em>f_printf</em>(&fil, "%04o", 255); <span class="c">/* "0377" */</span>
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<em>f_printf</em>(&fil, "%016b", 0x550F); <span class="c">/* "0101010100001111" */</span>
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<em>f_printf</em>(&fil, "%s", "String"); <span class="c">/* "String" */</span>
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<em>f_printf</em>(&fil, "%8s", "abc"); <span class="c">/* " abc" */</span>
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<em>f_printf</em>(&fil, "%-8s", "abc"); <span class="c">/* "abc " */</span>
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<em>f_printf</em>(&fil, "%c", 'a'); <span class="c">/* "a" */</span>
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<em>f_printf</em>(&fil, "%f", 10.0); <span class="c">/* f_printf lacks floating point support */</span>
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</pre>
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</div>
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<div class="para ref">
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<h4>See Also</h4>
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<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>
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</div>
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<p class="foot"><a href="../00index_e.html">Return</a></p>
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</body>
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</html>
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