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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 ‘<samp><span class="samp">%d</span></samp>’ 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 ‘<samp><span class="samp">%i</span></samp>’ 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 ‘<samp><span class="samp">#</span></samp>’ flag character with the |
| ‘<samp><span class="samp">%x</span></samp>’, ‘<samp><span class="samp">%o</span></samp>’, or ‘<samp><span class="samp">%d</span></samp>’ conversion. See <a href="Integer-Conversions.html#Integer-Conversions">Integer Conversions</a>.) |
| |
| <p>For example, any of the strings ‘<samp><span class="samp">10</span></samp>’, ‘<samp><span class="samp">0xa</span></samp>’, or ‘<samp><span class="samp">012</span></samp>’ |
| could be read in as integers under the ‘<samp><span class="samp">%i</span></samp>’ conversion. Each of |
| these specifies a number with decimal value <code>10</code>. |
| |
| <p>The ‘<samp><span class="samp">%o</span></samp>’, ‘<samp><span class="samp">%u</span></samp>’, and ‘<samp><span class="samp">%x</span></samp>’ 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 ‘<samp><span class="samp">%X</span></samp>’ conversion is identical to the ‘<samp><span class="samp">%x</span></samp>’ 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>‘<samp><span class="samp">hh</span></samp>’<dd>Specifies that the argument is a <code>signed char *</code> or <code>unsigned |
| char *</code>. |
| |
| <p>This modifier was introduced in ISO C99<!-- /@w -->. |
| |
| <br><dt>‘<samp><span class="samp">h</span></samp>’<dd>Specifies that the argument is a <code>short int *</code> or <code>unsigned |
| short int *</code>. |
| |
| <br><dt>‘<samp><span class="samp">j</span></samp>’<dd>Specifies that the argument is a <code>intmax_t *</code> or <code>uintmax_t *</code>. |
| |
| <p>This modifier was introduced in ISO C99<!-- /@w -->. |
| |
| <br><dt>‘<samp><span class="samp">l</span></samp>’<dd>Specifies that the argument is a <code>long int *</code> or <code>unsigned |
| long int *</code>. Two ‘<samp><span class="samp">l</span></samp>’ characters is like the ‘<samp><span class="samp">L</span></samp>’ modifier, below. |
| |
| <p>If used with ‘<samp><span class="samp">%c</span></samp>’ or ‘<samp><span class="samp">%s</span></samp>’ the corresponding parameter is |
| considered as a pointer to a wide character or wide character string |
| respectively. This use of ‘<samp><span class="samp">l</span></samp>’ was introduced in Amendment 1<!-- /@w --> to |
| ISO C90<!-- /@w -->. |
| |
| <br><dt>‘<samp><span class="samp">ll</span></samp>’<dt>‘<samp><span class="samp">L</span></samp>’<dt>‘<samp><span class="samp">q</span></samp>’<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 ‘<samp><span class="samp">q</span></samp>’ modifier is another name for the same thing, which comes |
| from 4.4 BSD; a <code>long long int</code><!-- /@w --> is sometimes called a “quad” |
| <code>int</code>. |
| |
| <br><dt>‘<samp><span class="samp">t</span></samp>’<dd>Specifies that the argument is a <code>ptrdiff_t *</code>. |
| |
| <p>This modifier was introduced in ISO C99<!-- /@w -->. |
| |
| <br><dt>‘<samp><span class="samp">z</span></samp>’<dd>Specifies that the argument is a <code>size_t *</code>. |
| |
| <p>This modifier was introduced in ISO C99<!-- /@w -->. |
| </dl> |
| |
| <p>All of the ‘<samp><span class="samp">%e</span></samp>’, ‘<samp><span class="samp">%f</span></samp>’, ‘<samp><span class="samp">%g</span></samp>’, ‘<samp><span class="samp">%E</span></samp>’, and ‘<samp><span class="samp">%G</span></samp>’ |
| 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>‘<samp><span class="samp">l</span></samp>’<dd>Specifies that the argument is of type <code>double *</code>. |
| |
| <br><dt>‘<samp><span class="samp">L</span></samp>’<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 ‘<samp><span class="samp">'</span></samp>’. 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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