'\" t .\" Copyright (c) Bruno Haible .\" .\" SPDX-License-Identifier: GPL-2.0-or-later .\" .\" References consulted: .\" GNU glibc-2 source code and manual .\" Dinkumware C library reference http://www.dinkumware.com/ .\" OpenGroup's Single UNIX specification http://www.UNIX-systems.org/online.html .\" ISO/IEC 9899:1999 .\" .TH mbtowc 3 2024-06-15 "Linux man-pages 6.9.1" .SH NAME mbtowc \- convert a multibyte sequence to a wide character .SH LIBRARY Standard C library .RI ( libc ", " \-lc ) .SH SYNOPSIS .nf .B #include .P .BI "int mbtowc(wchar_t *restrict " pwc ", const char " s "[restrict ." n "], \ size_t " n ); .fi .SH DESCRIPTION The main case for this function is when .I s is not NULL and .I pwc is not NULL. In this case, the .BR mbtowc () function inspects at most .I n bytes of the multibyte string starting at .IR s , extracts the next complete multibyte character, converts it to a wide character and stores it at .IR *pwc . It updates an internal shift state known only to the .BR mbtowc () function. If .I s does not point to a null byte (\[aq]\[rs]0\[aq]), it returns the number of bytes that were consumed from .IR s , otherwise it returns 0. .P If the .I n bytes starting at .I s do not contain a complete multibyte character, or if they contain an invalid multibyte sequence, .BR mbtowc () returns \-1. This can happen even if .I n >= .IR MB_CUR_MAX , if the multibyte string contains redundant shift sequences. .P A different case is when .I s is not NULL but .I pwc is NULL. In this case, the .BR mbtowc () function behaves as above, except that it does not store the converted wide character in memory. .P A third case is when .I s is NULL. In this case, .I pwc and .I n are ignored. The .BR mbtowc () function .\" The Dinkumware doc and the Single UNIX specification say this, but .\" glibc doesn't implement this. resets the shift state, only known to this function, to the initial state, and returns nonzero if the encoding has nontrivial shift state, or zero if the encoding is stateless. .SH RETURN VALUE If .I s is not NULL, the .BR mbtowc () function returns the number of consumed bytes starting at .IR s , or 0 if .I s points to a null byte, or \-1 upon failure. .P If .I s is NULL, the .BR mbtowc () function returns nonzero if the encoding has nontrivial shift state, or zero if the encoding is stateless. .SH ATTRIBUTES For an explanation of the terms used in this section, see .BR attributes (7). .TS allbox; lbx lb lb l l l. Interface Attribute Value T{ .na .nh .BR mbtowc () T} Thread safety MT-Unsafe race .TE .SH VERSIONS This function is not multithread safe. The function .BR mbrtowc (3) provides a better interface to the same functionality. .SH STANDARDS C11, POSIX.1-2008. .SH HISTORY POSIX.1-2001, C99. .SH NOTES The behavior of .BR mbtowc () depends on the .B LC_CTYPE category of the current locale. .SH SEE ALSO .BR MB_CUR_MAX (3), .BR mblen (3), .BR mbrtowc (3), .BR mbstowcs (3), .BR wcstombs (3), .BR wctomb (3)