.\"	$OpenBSD: ungetwc.3,v 1.4 2010/09/10 18:38:19 jmc Exp $
.\"
.\"	$NetBSD: ungetwc.3,v 1.7 2003/09/08 17:54:32 wiz Exp $
.\"
.\" Copyright (c) 1990, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
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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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.\"     @(#)ungetc.3	8.1 (Berkeley) 6/4/93
.\"
.Dd $Mdocdate: September 10 2010 $
.Dt UNGETWC 3
.Os
.Sh NAME
.Nm ungetwc
.Nd un-get wide character from input stream
.Sh SYNOPSIS
.In stdio.h
.In wchar.h
.Ft wint_t
.Fn ungetwc "wint_t wc" "FILE *stream"
.Sh DESCRIPTION
The
.Fn ungetwc
function pushes the wide character
.Fa wc
(converted to an wchar_t)
back onto the input stream pointed to by
.Fa stream .
The pushed-backed wide characters will be returned by subsequent reads on the
stream (in reverse order).
A successful intervening call, using the same stream, to one of the file
positioning functions
.Xr fseek 3 ,
.Xr fsetpos 3 ,
or
.Xr rewind 3
will discard the pushed back wide characters.
.Pp
One wide character of push-back is guaranteed,
but as long as there is
sufficient memory, an effectively infinite amount of pushback is allowed.
.Pp
If a character is successfully pushed back,
the end-of-file indicator for the stream is cleared.
.Sh RETURN VALUES
The
.Fn ungetwc
function
returns
the wide character pushed back after the conversion, or
.Dv WEOF
if the operation fails.
If the value of the argument
.Fa c
character equals
.Dv WEOF ,
the operation will fail and the stream will remain unchanged.
.Sh SEE ALSO
.Xr fseek 3 ,
.Xr getwc 3
.Sh STANDARDS
The
.Fn ungetwc
function conforms to
.St -isoC-99 .
.Sh BUGS
The current implementation uses a fixed sized ungetwc-buffer.