newlib-cygwin/newlib/libc/stdio/fileno.c

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/*
FUNCTION
<<fileno>>---return file descriptor associated with stream
INDEX
fileno
ANSI_SYNOPSIS
#include <stdio.h>
int fileno(FILE *<[fp]>);
TRAD_SYNOPSIS
#include <stdio.h>
int fileno(<[fp]>)
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.
*/
#include <stdio.h>
#include "local.h"
int
_DEFUN (fileno, (f),
FILE * f)
{
int result;
_flockfile(f);
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CHECK_INIT (f);
result = __sfileno (f);
_funlockfile(f);
return result;
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}