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.Dd March 3, 2004 35.Dt UNGETWC 3 36.Os 37.Sh NAME 38.Nm ungetwc 39.Nd un-get wide character from input stream 40.Sh LIBRARY 41.Lb libc 42.Sh SYNOPSIS 43.In stdio.h 44.In wchar.h 45.Ft wint_t 46.Fn ungetwc "wint_t wc" "FILE *stream" 47.Sh DESCRIPTION 48The 49.Fn ungetwc 50function pushes the wide character 51.Fa wc 52(converted to an 53.Vt wchar_t ) 54back onto the input stream pointed to by 55.Fa stream . 56The pushed-backed wide characters will be returned by subsequent reads on the 57stream (in reverse order). 58A successful intervening call, using the same stream, to one of the file 59positioning functions 60.Xr fseek 3 , 61.Xr fsetpos 3 , 62or 63.Xr rewind 3 64will discard the pushed back wide characters. 65.Pp 66One wide character of push-back is guaranteed, 67but as long as there is 68sufficient memory, an effectively infinite amount of pushback is allowed. 69.Pp 70If a character is successfully pushed-back, 71the end-of-file indicator for the stream is cleared. 72.Sh RETURN VALUES 73The 74.Fn ungetwc 75function 76returns 77the wide character pushed-back after the conversion, or 78.Dv WEOF 79if the operation fails. 80If the value of the argument 81.Fa c 82character equals 83.Dv WEOF , 84the operation will fail and the stream will remain unchanged. 85.Sh SEE ALSO 86.Xr fseek 3 , 87.Xr getwc 3 88.Sh STANDARDS 89The 90.Fn ungetwc 91function conforms to 92.St -isoC-99 . 93