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<title>GCC libquadmath: quadmath_snprintf</title>

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<a name="quadmath_005fsnprintf"></a>
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Previous: <a href="strtoflt128.html#strtoflt128" accesskey="p" rel="prev">strtoflt128</a>, Up: <a href="I_002fO-Library-Routines.html#I_002fO-Library-Routines" accesskey="u" rel="up">I/O Library Routines</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p>
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<a name="quadmath_005fsnprintf-_002d_002d_002d-Convert-to-string"></a>
<h3 class="section">3.2 <code>quadmath_snprintf</code> &mdash; Convert to string</h3>

<p>The function <code>quadmath_snprintf</code> converts a <code>__float128</code> floating-point
number into a string.  It is a specialized alternative to <code>snprintf</code>, where
the format string is restricted to a single conversion specifier with <code>Q</code>
modifier and conversion specifier <code>e</code>, <code>E</code>, <code>f</code>, <code>F</code>, <code>g</code>,
<code>G</code>, <code>a</code> or <code>A</code>, with no extra characters before or after the
conversion specifier.  The <code>%m$</code> or <code>*m$</code> style must not be used in
the format.
</p>
<dl compact="compact">
<dt>Syntax</dt>
<dd><p><code>int quadmath_snprintf (char *s, size_t size, const char *format, ...)</code>
</p>
</dd>
<dt><em>Arguments</em>:</dt>
<dd><table>
<tr><td width="15%"><var>s</var></td><td width="70%">output string</td></tr>
<tr><td width="15%"><var>size</var></td><td width="70%">byte size of the string, including tailing NUL</td></tr>
<tr><td width="15%"><var>format</var></td><td width="70%">conversion specifier string</td></tr>
</table>

</dd>
<dt>Note</dt>
<dd><p>On some targets when supported by the C library hooks are installed
for <code>printf</code> family of functions, so that <code>printf (&quot;%Qe&quot;, 1.2Q);</code>
etc. works too.
</p>
</dd>
<dt>Example</dt>
<dd><div class="smallexample">
<pre class="smallexample">#include &lt;quadmath.h&gt;
#include &lt;stdlib.h&gt;
#include &lt;stdio.h&gt;

int main ()
{
  __float128 r;
  int prec = 20;
  int width = 46;
  char buf[128];

  r = 2.0q;
  r = sqrtq (r);
  int n = quadmath_snprintf (buf, sizeof buf, &quot;%+-#*.20Qe&quot;, width, r);
  if ((size_t) n &lt; sizeof buf)
    printf (&quot;%s\n&quot;, buf);
    /* Prints: +1.41421356237309504880e+00 */
  quadmath_snprintf (buf, sizeof buf, &quot;%Qa&quot;, r);
  if ((size_t) n &lt; sizeof buf)
    printf (&quot;%s\n&quot;, buf);
    /* Prints: 0x1.6a09e667f3bcc908b2fb1366ea96p+0 */
  n = quadmath_snprintf (NULL, 0, &quot;%+-#46.*Qe&quot;, prec, r);
  if (n &gt; -1)
    {
      char *str = malloc (n + 1);
      if (str)
        {
          quadmath_snprintf (str, n + 1, &quot;%+-#46.*Qe&quot;, prec, r);
          printf (&quot;%s\n&quot;, str);
          /* Prints: +1.41421356237309504880e+00 */
        }
      free (str);
    }
  return 0;
}
</pre></div>

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