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.\" 40.Dd October 24, 2001 41.Dt UNGETWC 3 42.Os 43.Sh NAME 44.Nm ungetwc 45.Nd un-get wide-character from input stream 46.Sh LIBRARY 47.Lb libc 48.Sh SYNOPSIS 49.Fd #include \*[Lt]stdio.h\*[Gt] 50.Fd #include \*[Lt]wchar.h\*[Gt] 51.Ft wint_t 52.Fn ungetwc "wint_t wc" "FILE *stream" 53.Sh DESCRIPTION 54The 55.Fn ungetwc 56function pushes the wide-character 57.Fa wc 58(converted to an wchar_t) 59back onto the input stream pointed to by 60.Fa stream . 61The pushed-backed wide-characters will be returned by subsequent reads on the 62stream (in reverse order). 63A successful intervening call, using the same stream, to one of the file 64positioning functions 65.Xr fseek 3 , 66.Xr fsetpos 3 , 67or 68.Xr rewind 3 69will discard the pushed back wide-characters. 70.Pp 71One wide-character of push-back is guaranteed, 72but as long as there is 73sufficient memory, an effectively infinite amount of pushback is allowed. 74.Pp 75If a character is successfully pushed-back, 76the end-of-file indicator for the stream is cleared. 77.Sh RETURN VALUES 78The 79.Fn ungetwc 80function 81returns 82the wide-character pushed-back after the conversion, or 83.Dv WEOF 84if the operation fails. 85If the value of the argument 86.Fa c 87character equals 88.Dv WEOF , 89the operation will fail and the stream will remain unchanged. 90.Sh SEE ALSO 91.Xr fseek 3 , 92.Xr getwc 3 93.Sh STANDARDS 94The 95.Fn ungetwc 96function conforms to 97.St -isoC99 . 98.Sh BUGS 99The current implementation uses a fixed sized ungetwc-buffer. 100