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: head/lib/libc/stdio/ungetwc.3 165903 2007-01-09 00:28:16Z imp $ 36.\" 37.Dd December 26, 2013 38.Dt UNGETWC 3 39.Os 40.Sh NAME 41.Nm ungetwc , 42.Nm ungetwc_l 43.Nd un-get wide character from input stream 44.Sh LIBRARY 45.Lb libc 46.Sh SYNOPSIS 47.In stdio.h 48.In wchar.h 49.Ft wint_t 50.Fn ungetwc "wint_t wc" "FILE *stream" 51.In xlocale.h 52.Ft wint_t 53.Fn ungetwc_l "wint_t wc" "FILE *stream" "locale_t locale" 54.Sh DESCRIPTION 55The 56.Fn ungetwc 57and 58.Fn ungetwc_l 59functions push the wide character 60.Fa wc 61(converted to an 62.Vt wchar_t ) 63back onto the input stream pointed to by 64.Fa stream . 65The pushed-backed wide characters will be returned by subsequent reads on the 66stream (in reverse order). 67A successful intervening call, using the same stream, to one of the file 68positioning functions 69.Xr fseek 3 , 70.Xr fsetpos 3 , 71or 72.Xr rewind 3 73will discard the pushed back wide characters. 74.Pp 75One wide character of push-back is guaranteed, 76but as long as there is 77sufficient memory, an effectively infinite amount of pushback is allowed. 78.Pp 79If a character is successfully pushed-back, 80the end-of-file indicator for the stream is cleared. 81.Pp 82The 83.Fn ungetwc_l 84function takes an explicit 85.Fa locale 86argument, whereas the 87.Fn ungetwc 88function uses the current global or per-thread locale. 89.Sh RETURN VALUES 90The 91.Fn ungetwc 92and 93.Fn ungetwc_l 94functions return the wide character pushed-back after the conversion, or 95.Dv WEOF 96if the operation fails. 97If the value of the argument 98.Fa c 99character equals 100.Dv WEOF , 101the operation will fail and the stream will remain unchanged. 102.Sh SEE ALSO 103.Xr fseek 3 , 104.Xr getwc 3 , 105.Xr xlocale 3 106.Sh STANDARDS 107The 108.Fn ungetwc 109function conforms to 110.St -isoC-99 . 111