1.\" Copyright (c) 2002-2004 Tim J. Robbins. All rights reserved. 2.\" Copyright (c) 1993 3.\" The Regents of the University of California. All rights reserved. 4.\" 5.\" This code is derived from software contributed to Berkeley by 6.\" Donn Seeley of BSDI. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 3. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)multibyte.3 8.1 (Berkeley) 6/4/93 33.\" 34.Dd September 9, 2019 35.Dt MULTIBYTE 3 36.Os 37.Sh NAME 38.Nm multibyte 39.Nd multibyte and wide character manipulation functions 40.Sh LIBRARY 41.Lb libc 42.Sh SYNOPSIS 43.In limits.h 44.In stdlib.h 45.In wchar.h 46.Sh DESCRIPTION 47The basic elements of some written natural languages, such as Chinese, 48cannot be represented uniquely with single C 49.Vt char Ns s . 50The C standard supports two different ways of dealing with 51extended natural language encodings: 52wide characters and 53multibyte characters. 54Wide characters are an internal representation 55which allows each basic element to map 56to a single object of type 57.Vt wchar_t . 58Multibyte characters are used for input and output 59and code each basic element as a sequence of C 60.Vt char Ns s . 61Individual basic elements may map into one or more 62(up to 63.Dv MB_LEN_MAX ) 64bytes in a multibyte character. 65.Pp 66The current locale 67.Pq Xr setlocale 3 68governs the interpretation of wide and multibyte characters. 69The locale category 70.Dv LC_CTYPE 71specifically controls this interpretation. 72The 73.Vt wchar_t 74type is wide enough to hold the largest value 75in the wide character representations for all locales. 76.Pp 77Multibyte strings may contain 78.Sq shift 79indicators to switch to and from 80particular modes within the given representation. 81If explicit bytes are used to signal shifting, 82these are not recognized as separate characters 83but are lumped with a neighboring character. 84There is always a distinguished 85.Sq initial 86shift state. 87Some functions (e.g., 88.Xr mblen 3 , 89.Xr mbtowc 3 90and 91.Xr wctomb 3 ) 92maintain static shift state internally, whereas 93others store it in an 94.Vt mbstate_t 95object passed by the caller. 96Shift states are undefined after a call to 97.Xr setlocale 3 98with the 99.Dv LC_CTYPE 100or 101.Dv LC_ALL 102categories. 103.Pp 104For convenience in processing, 105the wide character with value 0 106(the null wide character) 107is recognized as the wide character string terminator, 108and the character with value 0 109(the null byte) 110is recognized as the multibyte character string terminator. 111Null bytes are not permitted within multibyte characters. 112.Pp 113The C library provides the following functions for dealing with 114multibyte characters: 115.Bl -column "Description" 116.It Sy "Function Description" 117.It Xr mblen 3 Ta "get number of bytes in a character" 118.It Xr mbrlen 3 Ta "get number of bytes in a character (restartable)" 119.It Xr mbrtowc 3 Ta "convert a character to a wide-character code (restartable)" 120.It Xr mbsrtowcs 3 Ta "convert a character string to a wide-character string (restartable)" 121.It Xr mbstowcs 3 Ta "convert a character string to a wide-character string" 122.It Xr mbtowc 3 Ta "convert a character to a wide-character code" 123.It Xr wcrtomb 3 Ta "convert a wide-character code to a character (restartable)" 124.It Xr wcstombs 3 Ta "convert a wide-character string to a character string" 125.It Xr wcsrtombs 3 Ta "convert a wide-character string to a character string (restartable)" 126.It Xr wctomb 3 Ta "convert a wide-character code to a character" 127.El 128.Sh SEE ALSO 129.Xr localedef 1 , 130.Xr setlocale 3 , 131.Xr stdio 3 , 132.Xr big5 5 , 133.Xr euc 5 , 134.Xr gb18030 5 , 135.Xr gb2312 5 , 136.Xr gbk 5 , 137.Xr mskanji 5 , 138.Xr utf8 5 139.Sh STANDARDS 140These functions conform to 141.St -isoC-99 . 142