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4.15 fileno—return file descriptor associated with stream

Synopsis

#include <stdio.h>
int fileno(FILE *fp);

Description
You can use fileno to return the file descriptor identified by fp.


Returns
fileno returns a non-negative integer when successful. If fp is not an open stream, fileno returns -1.


Portability
fileno is not part of ANSI C. POSIX requires fileno.

Supporting OS subroutines required: none.