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| <h4 class="subsection">12.14.7 Other Input Conversions</h4> |
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| <p>This section describes the miscellaneous input conversions. |
| |
| <p>The ‘<samp><span class="samp">%p</span></samp>’ conversion is used to read a pointer value. It recognizes |
| the same syntax used by the ‘<samp><span class="samp">%p</span></samp>’ output conversion for |
| <code>printf</code> (see <a href="Other-Output-Conversions.html#Other-Output-Conversions">Other Output Conversions</a>); that is, a hexadecimal |
| number just as the ‘<samp><span class="samp">%x</span></samp>’ conversion accepts. The corresponding |
| argument should be of type <code>void **</code>; that is, the address of a |
| place to store a pointer. |
| |
| <p>The resulting pointer value is not guaranteed to be valid if it was not |
| originally written during the same program execution that reads it in. |
| |
| <p>The ‘<samp><span class="samp">%n</span></samp>’ conversion produces the number of characters read so far |
| by this call. The corresponding argument should be of type <code>int *</code>. |
| This conversion works in the same way as the ‘<samp><span class="samp">%n</span></samp>’ conversion for |
| <code>printf</code>; see <a href="Other-Output-Conversions.html#Other-Output-Conversions">Other Output Conversions</a>, for an example. |
| |
| <p>The ‘<samp><span class="samp">%n</span></samp>’ conversion is the only mechanism for determining the |
| success of literal matches or conversions with suppressed assignments. |
| If the ‘<samp><span class="samp">%n</span></samp>’ follows the locus of a matching failure, then no value |
| is stored for it since <code>scanf</code> returns before processing the |
| ‘<samp><span class="samp">%n</span></samp>’. If you store <code>-1</code> in that argument slot before calling |
| <code>scanf</code>, the presence of <code>-1</code> after <code>scanf</code> indicates an |
| error occurred before the ‘<samp><span class="samp">%n</span></samp>’ was reached. |
| |
| <p>Finally, the ‘<samp><span class="samp">%%</span></samp>’ conversion matches a literal ‘<samp><span class="samp">%</span></samp>’ character |
| in the input stream, without using an argument. This conversion does |
| not permit any flags, field width, or type modifier to be specified. |
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