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<h4 class="subsection">12.14.4 Numeric Input Conversions</h4>

<p>This section describes the <code>scanf</code> conversions for reading numeric
values.

   <p>The &lsquo;<samp><span class="samp">%d</span></samp>&rsquo; conversion matches an optionally signed integer in decimal
radix.  The syntax that is recognized is the same as that for the
<code>strtol</code> function (see <a href="Parsing-of-Integers.html#Parsing-of-Integers">Parsing of Integers</a>) with the value
<code>10</code> for the <var>base</var> argument.

   <p>The &lsquo;<samp><span class="samp">%i</span></samp>&rsquo; conversion matches an optionally signed integer in any of
the formats that the C language defines for specifying an integer
constant.  The syntax that is recognized is the same as that for the
<code>strtol</code> function (see <a href="Parsing-of-Integers.html#Parsing-of-Integers">Parsing of Integers</a>) with the value
<code>0</code> for the <var>base</var> argument.  (You can print integers in this
syntax with <code>printf</code> by using the &lsquo;<samp><span class="samp">#</span></samp>&rsquo; flag character with the
&lsquo;<samp><span class="samp">%x</span></samp>&rsquo;, &lsquo;<samp><span class="samp">%o</span></samp>&rsquo;, or &lsquo;<samp><span class="samp">%d</span></samp>&rsquo; conversion.  See <a href="Integer-Conversions.html#Integer-Conversions">Integer Conversions</a>.)

   <p>For example, any of the strings &lsquo;<samp><span class="samp">10</span></samp>&rsquo;, &lsquo;<samp><span class="samp">0xa</span></samp>&rsquo;, or &lsquo;<samp><span class="samp">012</span></samp>&rsquo;
could be read in as integers under the &lsquo;<samp><span class="samp">%i</span></samp>&rsquo; conversion.  Each of
these specifies a number with decimal value <code>10</code>.

   <p>The &lsquo;<samp><span class="samp">%o</span></samp>&rsquo;, &lsquo;<samp><span class="samp">%u</span></samp>&rsquo;, and &lsquo;<samp><span class="samp">%x</span></samp>&rsquo; conversions match unsigned
integers in octal, decimal, and hexadecimal radices, respectively.  The
syntax that is recognized is the same as that for the <code>strtoul</code>
function (see <a href="Parsing-of-Integers.html#Parsing-of-Integers">Parsing of Integers</a>) with the appropriate value
(<code>8</code>, <code>10</code>, or <code>16</code>) for the <var>base</var> argument.

   <p>The &lsquo;<samp><span class="samp">%X</span></samp>&rsquo; conversion is identical to the &lsquo;<samp><span class="samp">%x</span></samp>&rsquo; conversion.  They
both permit either uppercase or lowercase letters to be used as digits.

   <p>The default type of the corresponding argument for the <code>%d</code> and
<code>%i</code> conversions is <code>int *</code>, and <code>unsigned int *</code> for the
other integer conversions.  You can use the following type modifiers to
specify other sizes of integer:

     <dl>
<dt>&lsquo;<samp><span class="samp">hh</span></samp>&rsquo;<dd>Specifies that the argument is a <code>signed char *</code> or <code>unsigned
char *</code>.

     <p>This modifier was introduced in ISO&nbsp;C99<!-- /@w -->.

     <br><dt>&lsquo;<samp><span class="samp">h</span></samp>&rsquo;<dd>Specifies that the argument is a <code>short int *</code> or <code>unsigned
short int *</code>.

     <br><dt>&lsquo;<samp><span class="samp">j</span></samp>&rsquo;<dd>Specifies that the argument is a <code>intmax_t *</code> or <code>uintmax_t *</code>.

     <p>This modifier was introduced in ISO&nbsp;C99<!-- /@w -->.

     <br><dt>&lsquo;<samp><span class="samp">l</span></samp>&rsquo;<dd>Specifies that the argument is a <code>long int *</code> or <code>unsigned
long int *</code>.  Two &lsquo;<samp><span class="samp">l</span></samp>&rsquo; characters is like the &lsquo;<samp><span class="samp">L</span></samp>&rsquo; modifier, below.

     <p>If used with &lsquo;<samp><span class="samp">%c</span></samp>&rsquo; or &lsquo;<samp><span class="samp">%s</span></samp>&rsquo; the corresponding parameter is
considered as a pointer to a wide character or wide character string
respectively.  This use of &lsquo;<samp><span class="samp">l</span></samp>&rsquo; was introduced in Amendment&nbsp;1<!-- /@w --> to
ISO&nbsp;C90<!-- /@w -->.

     <br><dt>&lsquo;<samp><span class="samp">ll</span></samp>&rsquo;<dt>&lsquo;<samp><span class="samp">L</span></samp>&rsquo;<dt>&lsquo;<samp><span class="samp">q</span></samp>&rsquo;<dd>Specifies that the argument is a <code>long long int *</code> or <code>unsigned long long int *</code>.  (The <code>long long</code> type is an extension supported by the
GNU C compiler.  For systems that don't provide extra-long integers, this
is the same as <code>long int</code>.)

     <p>The &lsquo;<samp><span class="samp">q</span></samp>&rsquo; modifier is another name for the same thing, which comes
from 4.4 BSD; a <code>long&nbsp;long&nbsp;int</code><!-- /@w --> is sometimes called a &ldquo;quad&rdquo;
<code>int</code>.

     <br><dt>&lsquo;<samp><span class="samp">t</span></samp>&rsquo;<dd>Specifies that the argument is a <code>ptrdiff_t *</code>.

     <p>This modifier was introduced in ISO&nbsp;C99<!-- /@w -->.

     <br><dt>&lsquo;<samp><span class="samp">z</span></samp>&rsquo;<dd>Specifies that the argument is a <code>size_t *</code>.

     <p>This modifier was introduced in ISO&nbsp;C99<!-- /@w -->. 
</dl>

   <p>All of the &lsquo;<samp><span class="samp">%e</span></samp>&rsquo;, &lsquo;<samp><span class="samp">%f</span></samp>&rsquo;, &lsquo;<samp><span class="samp">%g</span></samp>&rsquo;, &lsquo;<samp><span class="samp">%E</span></samp>&rsquo;, and &lsquo;<samp><span class="samp">%G</span></samp>&rsquo;
input conversions are interchangeable.  They all match an optionally
signed floating point number, in the same syntax as for the
<code>strtod</code> function (see <a href="Parsing-of-Floats.html#Parsing-of-Floats">Parsing of Floats</a>).

   <p>For the floating-point input conversions, the default argument type is
<code>float *</code>.  (This is different from the corresponding output
conversions, where the default type is <code>double</code>; remember that
<code>float</code> arguments to <code>printf</code> are converted to <code>double</code>
by the default argument promotions, but <code>float *</code> arguments are
not promoted to <code>double *</code>.)  You can specify other sizes of float
using these type modifiers:

     <dl>
<dt>&lsquo;<samp><span class="samp">l</span></samp>&rsquo;<dd>Specifies that the argument is of type <code>double *</code>.

     <br><dt>&lsquo;<samp><span class="samp">L</span></samp>&rsquo;<dd>Specifies that the argument is of type <code>long double *</code>. 
</dl>

   <p>For all the above number parsing formats there is an additional optional
flag &lsquo;<samp><span class="samp">'</span></samp>&rsquo;.  When this flag is given the <code>scanf</code> function
expects the number represented in the input string to be formatted
according to the grouping rules of the currently selected locale
(see <a href="General-Numeric.html#General-Numeric">General Numeric</a>).

   <p>If the <code>"C"</code> or <code>"POSIX"</code> locale is selected there is no
difference.  But for a locale which specifies values for the appropriate
fields in the locale the input must have the correct form in the input. 
Otherwise the longest prefix with a correct form is processed.

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