1.\" $NetBSD: ungetwc.3,v 1.7 2003/09/08 17:54:32 wiz Exp $ 2.\" $DragonFly: src/lib/libc/stdio/ungetwc.3,v 1.1 2005/07/25 00:37:41 joerg Exp $ 3.\" 4.\" Copyright (c) 1990, 1991, 1993 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" This code is derived from software contributed to Berkeley by 8.\" Chris Torek and the American National Standards Committee X3, 9.\" on Information Processing Systems. 10.\" 11.\" Redistribution and use in source and binary forms, with or without 12.\" modification, are permitted provided that the following conditions 13.\" are met: 14.\" 1. Redistributions of source code must retain the above copyright 15.\" notice, this list of conditions and the following disclaimer. 16.\" 2. Redistributions in binary form must reproduce the above copyright 17.\" notice, this list of conditions and the following disclaimer in the 18.\" documentation and/or other materials provided with the distribution. 19.\" 3. Neither the name of the University nor the names of its contributors 20.\" may be used to endorse or promote products derived from this software 21.\" without specific prior written permission. 22.\" 23.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33.\" SUCH DAMAGE. 34.\" 35.\" @(#)ungetc.3 8.1 (Berkeley) 6/4/93 36.\" 37.Dd October 24, 2001 38.Dt UNGETWC 3 39.Os 40.Sh NAME 41.Nm ungetwc 42.Nd un-get wide-character from input stream 43.Sh LIBRARY 44.Lb libc 45.Sh SYNOPSIS 46.In stdio.h 47.In wchar.h 48.Ft wint_t 49.Fn ungetwc "wint_t wc" "FILE *stream" 50.Sh DESCRIPTION 51The 52.Fn ungetwc 53function pushes the wide-character 54.Fa wc 55(converted to an wchar_t) 56back onto the input stream pointed to by 57.Fa stream . 58The pushed-backed wide-characters will be returned by subsequent reads on the 59stream (in reverse order). 60A successful intervening call, using the same stream, to one of the file 61positioning functions 62.Xr fseek 3 , 63.Xr fsetpos 3 , 64or 65.Xr rewind 3 66will discard the pushed back wide-characters. 67.Pp 68One wide-character of push-back is guaranteed, 69but as long as there is 70sufficient memory, an effectively infinite amount of pushback is allowed. 71.Pp 72If a character is successfully pushed-back, 73the end-of-file indicator for the stream is cleared. 74.Sh RETURN VALUES 75The 76.Fn ungetwc 77function 78returns 79the wide-character pushed-back after the conversion, or 80.Dv WEOF 81if the operation fails. 82If the value of the argument 83.Fa c 84character equals 85.Dv WEOF , 86the operation will fail and the stream will remain unchanged. 87.Sh SEE ALSO 88.Xr fseek 3 , 89.Xr getwc 3 90.Sh STANDARDS 91The 92.Fn ungetwc 93function conforms to 94.St -isoC-99 . 95.Sh BUGS 96The current implementation uses a fixed sized ungetwc-buffer. 97