.\"	$NetBSD: ferror.3,v 1.14 2010/05/08 11:35:14 wiz Exp $
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.\" This code is derived from software contributed to Berkeley by
.\" Chris Torek and the American National Standards Committee X3,
.\" on Information Processing Systems.
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.\"     @(#)ferror.3	8.2 (Berkeley) 4/19/94
.\"
.Dd May 6, 2010
.Dt FERROR 3
.Os
.Sh NAME
.Nm clearerr ,
.Nm feof ,
.Nm ferror ,
.Nm fileno
.Nd check and reset stream status
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In stdio.h
.Ft void
.Fn clearerr "FILE *stream"
.Ft int
.Fn feof "FILE *stream"
.Ft int
.Fn ferror "FILE *stream"
.Ft int
.Fn fileno "FILE *stream"
.Sh DESCRIPTION
The function
.Fn clearerr
clears the end-of-file and error indicators for the stream pointed
to by
.Fa stream .
.Pp
The function
.Fn feof
tests the end-of-file indicator for the stream pointed to by
.Fa stream ,
returning non-zero if it is set.
The end-of-file indicator can only be cleared by the function
.Fn clearerr .
.Pp
The function
.Fn ferror
tests the error indicator for the stream pointed to by
.Fa stream ,
returning non-zero if it is set.
The error indicator can only be reset by the
.Fn clearerr
function.
.Pp
The function
.Fn fileno
examines the argument
.Fa stream
and returns its integer descriptor.
.Sh ERRORS
The functions
.Fn clearerr ,
.Fn feof ,
and
.Fn ferror
should neither fail nor set the external variable
.Va errno .
However, the function
.Fn fileno
may fail and return \-1 in case the argument
.Fa stream
is not associated with a valid file descriptor.
(In this case the
.Nx
implementation does not follow the optional
.Tn POSIX
recommendation to set the
.Va errno
variable to
.Er EBADF . )
.Sh SEE ALSO
.Xr open 2 ,
.Xr stdio 3
.Sh STANDARDS
The functions
.Fn clearerr ,
.Fn feof ,
and
.Fn ferror
conform to
.St -ansiC .
The function
.Fn fileno
conforms to
.St -p1003.1-90 .