mirror of https://github.com/mkerrisk/man-pages
199 lines
3.7 KiB
Groff
199 lines
3.7 KiB
Groff
.\" Copyright (c) Bruno Haible <haible@clisp.cons.org>
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.\"
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.\" %%%LICENSE_START(GPLv2+_DOC_ONEPARA)
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.\" This is free documentation; you can redistribute it and/or
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.\" modify it under the terms of the GNU General Public License as
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.\" published by the Free Software Foundation; either version 2 of
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.\" the License, or (at your option) any later version.
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.\" %%%LICENSE_END
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.\"
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.\" References consulted:
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.\" GNU glibc-2 source code and manual
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.\" Dinkumware C library reference http://www.dinkumware.com/
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.\" OpenGroup's Single UNIX specification
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.\" http://www.UNIX-systems.org/online.html
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.\" ISO/IEC 9899:1999
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.\"
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.TH MBRTOWC 3 2019-03-06 "GNU" "Linux Programmer's Manual"
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.SH NAME
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mbrtowc \- convert a multibyte sequence to a wide character
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.SH SYNOPSIS
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.nf
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.B #include <wchar.h>
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.PP
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.BI "size_t mbrtowc(wchar_t *" pwc ", const char *" s ", size_t " n \
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", mbstate_t *" ps );
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.fi
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.SH DESCRIPTION
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The main case for this function is when
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.IR s
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is not NULL and
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.I pwc
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is
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not NULL.
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In this case, the
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.BR mbrtowc ()
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function inspects at most
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.I n
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bytes of the multibyte string starting at
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.IR s ,
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extracts the next complete
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multibyte character, converts it to a wide character and stores it at
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.IR *pwc .
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It updates the shift state
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.IR *ps .
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If the converted wide
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character is not L\(aq\e0\(aq (the null wide character),
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it returns the number of bytes that were consumed
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from
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.IR s .
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If the converted wide character is L\(aq\e0\(aq, it resets the shift
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state
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.I *ps
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to the initial state and returns 0.
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.PP
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If the
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.IR n
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bytes starting at
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.I s
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do not contain a complete multibyte
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character,
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.BR mbrtowc ()
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returns
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.IR "(size_t)\ \-2" .
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This can happen even if
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.I n
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>=
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.IR MB_CUR_MAX ,
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if the multibyte string contains redundant shift
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sequences.
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.PP
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If the multibyte string starting at
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.I s
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contains an invalid multibyte
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sequence before the next complete character,
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.BR mbrtowc ()
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returns
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.IR "(size_t)\ \-1"
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and sets
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.I errno
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to
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.BR EILSEQ .
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In this case,
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the effects on
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.I *ps
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are undefined.
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.PP
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A different case is when
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.IR s
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is not NULL but
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.I pwc
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is NULL.
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In this case, the
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.BR mbrtowc ()
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function behaves as above, except that it does not
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store the converted wide character in memory.
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.PP
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A third case is when
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.I s
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is NULL.
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In this case,
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.IR pwc
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and
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.I n
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are
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ignored.
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If the conversion state represented by
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.I *ps
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denotes an
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incomplete multibyte character conversion, the
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.BR mbrtowc ()
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function
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returns
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.IR "(size_t)\ \-1" ,
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sets
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.I errno
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to
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.BR EILSEQ ,
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and
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leaves
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.I *ps
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in an undefined state.
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Otherwise, the
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.BR mbrtowc ()
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function
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puts
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.I *ps
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in the initial state and returns 0.
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.PP
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In all of the above cases, if
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.I ps
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is NULL, a static anonymous
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state known only to the
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.BR mbrtowc ()
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function is used instead.
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Otherwise,
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.IR *ps
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must be a valid
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.I mbstate_t
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object.
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An
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.IR mbstate_t
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object
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.I a
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can be initialized to the initial state
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by zeroing it, for example using
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.PP
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.in +4n
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.EX
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memset(&a, 0, sizeof(a));
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.EE
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.in
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.SH RETURN VALUE
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The
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.BR mbrtowc ()
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function returns the number of bytes parsed from the
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multibyte sequence starting at
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.IR s ,
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if a non-L\(aq\e0\(aq wide character
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was recognized.
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It returns 0, if a L\(aq\e0\(aq wide character was recognized.
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It returns
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.I (size_t)\ \-1
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and sets
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.I errno
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to
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.BR EILSEQ ,
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if an invalid multibyte sequence was
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encountered.
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It returns
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.I "(size_t)\ \-2"
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if it couldn't parse a complete multibyte
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character, meaning that
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.I n
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should be increased.
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.SH ATTRIBUTES
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For an explanation of the terms used in this section, see
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.BR attributes (7).
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.TS
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allbox;
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lb lb lb
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l l l.
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Interface Attribute Value
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T{
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.BR mbrtowc ()
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T} Thread safety MT-Unsafe race:mbrtowc/!ps
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.TE
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.SH CONFORMING TO
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POSIX.1-2001, POSIX.1-2008, C99.
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.SH NOTES
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The behavior of
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.BR mbrtowc ()
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depends on the
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.B LC_CTYPE
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category of the
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current locale.
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.SH SEE ALSO
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.BR mbsinit (3),
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.BR mbsrtowcs (3)
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