Libc-825.40.1.tar.gz

[apple/libc.git] / stdio / FreeBSD / ungetwc.3

.\"	$NetBSD: ungetwc.3,v 1.3 2002/02/07 07:00:27 ross Exp $
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.\"     @(#)ungetc.3	8.1 (Berkeley) 6/4/93
.\" $FreeBSD: src/lib/libc/stdio/ungetwc.3,v 1.6 2007/01/09 00:28:07 imp Exp $
.\"
.Dd March 3, 2004
.Dt UNGETWC 3
.Os
.Sh NAME
.Nm ungetwc ,
.Nm ungetwc_l
.Nd un-get wide character from input stream
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In stdio.h
.In wchar.h
.Ft wint_t
.Fo ungetwc
.Fa "wint_t wc"
.Fa "FILE *stream"
.Fc
.In stdio.h
.In wchar.h
.In xlocale.h
.Ft wint_t
.Fo ungetwc_l
.Fa "wint_t wc"
.Fa "FILE *stream"
.Fa "locale_t loc"
.Fc
.Sh DESCRIPTION
The
.Fn ungetwc
function pushes the wide character
.Fa wc
(converted to an
.Vt wchar_t )
back onto the input stream pointed to by
.Fa stream .
The pushed-backed wide characters will be returned (in reverse order)
by subsequent reads on the stream.
A successful intervening call to one of the file
positioning functions
.Xr fseek 3 ,
.Xr fsetpos 3 ,
or
.Xr rewind 3 ,
using the same stream,
will discard the pushed-back wide characters.
.Pp
Only one wide character of push-back is guaranteed,
but as long as there is sufficient memory,
an effectively infinite amount of push-back is allowed.
.Pp
If a character is successfully pushed-back,
the end-of-file indicator for the stream is cleared.
.Pp
Although the
.Fn ungetwc
function uses the current locale, the
.Fn ungetwc_l
function may be passed a locale directly. See
.Xr xlocale 3
for more information.
.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 ,
.Xr xlocale 3
.Sh STANDARDS
The
.Fn ungetwc
function conforms to
.St -isoC-99 .