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| <h3 class="section">4.15 <code>fileno</code>—return file descriptor associated with stream</h3> |
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| <p><a name="index-fileno-176"></a><strong>Synopsis</strong> |
| <pre class="example"> #include <stdio.h> |
| int fileno(FILE *<var>fp</var>); |
| |
| </pre> |
| <p><strong>Description</strong><br> |
| You can use <code>fileno</code> to return the file descriptor identified by <var>fp</var>. |
| |
| <p><br> |
| <strong>Returns</strong><br> |
| <code>fileno</code> returns a non-negative integer when successful. |
| If <var>fp</var> is not an open stream, <code>fileno</code> returns -1. |
| |
| <p><br> |
| <strong>Portability</strong><br> |
| <code>fileno</code> is not part of ANSI C. |
| POSIX requires <code>fileno</code>. |
| |
| <p>Supporting OS subroutines required: none. |
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