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| <h3 class="section">3.1 <code>isalnum</code>—alphanumeric character predicate</h3> |
| |
| <p><a name="index-isalnum-110"></a><strong>Synopsis</strong> |
| <pre class="example"> #include <ctype.h> |
| int isalnum(int <var>c</var>); |
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| </pre> |
| <p><strong>Description</strong><br> |
| <code>isalnum</code> is a macro which classifies ASCII integer values by table |
| lookup. It is a predicate returning non-zero for alphabetic or |
| numeric ASCII characters, and <code>0</code> for other arguments. It is defined |
| only if <var>c</var> is representable as an unsigned char or if <var>c</var> is EOF. |
| |
| <p>You can use a compiled subroutine instead of the macro definition by |
| undefining the macro using `<code>#undef isalnum</code>'. |
| |
| <p><br> |
| <strong>Returns</strong><br> |
| <code>isalnum</code> returns non-zero if <var>c</var> is a letter (<code>a</code>–<code>z</code> or |
| <code>A</code>–<code>Z</code>) or a digit (<code>0</code>–<code>9</code>). |
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| <p><br> |
| <strong>Portability</strong><br> |
| <code>isalnum</code> is ANSI C. |
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| <p>No OS subroutines are required. |
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