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. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)ungetc.3 8.1 (Berkeley) 6/4/93 35.\" $FreeBSD$ 36.\" 37.Dd March 3, 2004 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 56.Vt wchar_t ) 57back onto the input stream pointed to by 58.Fa stream . 59The pushed-backed wide characters will be returned by subsequent reads on the 60stream (in reverse order). 61A successful intervening call, using the same stream, to one of the file 62positioning functions 63.Xr fseek 3 , 64.Xr fsetpos 3 , 65or 66.Xr rewind 3 67will discard the pushed back wide characters. 68.Pp 69One wide character of push-back is guaranteed, 70but as long as there is 71sufficient memory, an effectively infinite amount of pushback is allowed. 72.Pp 73If a character is successfully pushed-back, 74the end-of-file indicator for the stream is cleared. 75.Sh RETURN VALUES 76The 77.Fn ungetwc 78function 79returns 80the wide character pushed-back after the conversion, or 81.Dv WEOF 82if the operation fails. 83If the value of the argument 84.Fa c 85character equals 86.Dv WEOF , 87the operation will fail and the stream will remain unchanged. 88.Sh SEE ALSO 89.Xr fseek 3 , 90.Xr getwc 3 91.Sh STANDARDS 92The 93.Fn ungetwc 94function conforms to 95.St -isoC-99 . 96