1.\" $NetBSD: ungetwc.3,v 1.3 2002/02/07 07:00:27 ross Exp $ 2.\" 3.\" Copyright (c) 1990, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" This code is derived from software contributed to Berkeley by 7.\" Chris Torek and the American National Standards Committee X3, 8.\" on Information Processing Systems. 9.\" 10.\" Redistribution and use in source and binary forms, with or without 11.\" modification, are permitted provided that the following conditions 12.\" are met: 13.\" 1. Redistributions of source code must retain the above copyright 14.\" notice, this list of conditions and the following disclaimer. 15.\" 2. Redistributions in binary form must reproduce the above copyright 16.\" notice, this list of conditions and the following disclaimer in the 17.\" documentation and/or other materials provided with the distribution. 18.\" 3. All advertising materials mentioning features or use of this software 19.\" must display the following acknowledgement: 20.\" This product includes software developed by the University of 21.\" California, Berkeley and its contributors. 22.\" 4. Neither the name of the University nor the names of its contributors 23.\" may be used to endorse or promote products derived from this software 24.\" without specific prior written permission. 25.\" 26.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36.\" SUCH DAMAGE. 37.\" 38.\" @(#)ungetc.3 8.1 (Berkeley) 6/4/93 39.\" $FreeBSD$ 40.\" 41.Dd March 3, 2004 42.Dt UNGETWC 3 43.Os 44.Sh NAME 45.Nm ungetwc 46.Nd un-get wide character from input stream 47.Sh LIBRARY 48.Lb libc 49.Sh SYNOPSIS 50.In stdio.h 51.In wchar.h 52.Ft wint_t 53.Fn ungetwc "wint_t wc" "FILE *stream" 54.Sh DESCRIPTION 55The 56.Fn ungetwc 57function pushes the wide character 58.Fa wc 59(converted to an 60.Vt wchar_t ) 61back onto the input stream pointed to by 62.Fa stream . 63The pushed-backed wide characters will be returned by subsequent reads on the 64stream (in reverse order). 65A successful intervening call, using the same stream, to one of the file 66positioning functions 67.Xr fseek 3 , 68.Xr fsetpos 3 , 69or 70.Xr rewind 3 71will discard the pushed back wide characters. 72.Pp 73One wide character of push-back is guaranteed, 74but as long as there is 75sufficient memory, an effectively infinite amount of pushback is allowed. 76.Pp 77If a character is successfully pushed-back, 78the end-of-file indicator for the stream is cleared. 79.Sh RETURN VALUES 80The 81.Fn ungetwc 82function 83returns 84the wide character pushed-back after the conversion, or 85.Dv WEOF 86if the operation fails. 87If the value of the argument 88.Fa c 89character equals 90.Dv WEOF , 91the operation will fail and the stream will remain unchanged. 92.Sh SEE ALSO 93.Xr fseek 3 , 94.Xr getwc 3 95.Sh STANDARDS 96The 97.Fn ungetwc 98function conforms to 99.St -isoC-99 . 100