man3/wcstombs.3

.\" Copyright (c) Bruno Haible <haible@clisp.cons.org>
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.\" References consulted:
.\"   GNU glibc-2 source code and manual
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.TH WCSTOMBS 3  2019-03-06 "GNU" "Linux Programmer's Manual"
.SH NAME
wcstombs \- convert a wide-character string to a multibyte string
.SH SYNOPSIS
.nf
.B #include <stdlib.h>
.PP
.BI "size_t wcstombs(char *" dest ", const wchar_t *" src ", size_t " n );
.fi
.SH DESCRIPTION
If
.I dest
is not NULL, the
.BR wcstombs ()
function converts
the wide-character string
.I src
to a multibyte string starting at
.IR dest .
At most
.I n
bytes are written to
.IR dest .
The sequence of characters placed in
.IR dest
begins in the initial shift state.
The conversion can stop for three reasons:
.IP 1. 3
A wide character has been encountered that can not be represented as a
multibyte sequence (according to the current locale).
In this case,
.I (size_t)\ \-1
is returned.
.IP 2.
The length limit forces a stop.
In this case, the number of bytes written to
.I dest
is returned, but the shift state at this point is lost.
.IP 3.
The wide-character string has been completely converted, including the
terminating null wide character (L\(aq\e0\(aq).
In this case, the conversion ends in the initial shift state.
The number of bytes written to
.IR dest ,
excluding the terminating null byte (\(aq\e0\(aq), is returned.
.PP
The programmer must ensure that there is room for at least
.I n
bytes
at
.IR dest .
.PP
If
.IR dest
is NULL,
.I n
is ignored, and the conversion proceeds as
above, except that the converted bytes are not written out to memory,
and no length limit exists.
.PP
In order to avoid the case 2 above, the programmer should make sure
.I n
is greater than or equal to
.IR "wcstombs(NULL,src,0)+1" .
.SH RETURN VALUE
The
.BR wcstombs ()
function returns the number of bytes that make up the
converted part of a multibyte sequence,
not including the terminating null byte.
If a wide character was encountered which could not be
converted,
.I (size_t)\ \-1
is returned.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lb lb lb
l l l.
Interface	Attribute	Value
T{
.BR wcstombs ()
T}	Thread safety	MT-Safe
.TE
.sp 1
.SH CONFORMING TO
POSIX.1-2001, POSIX.1-2008, C99.
.SH NOTES
The behavior of
.BR wcstombs ()
depends on the
.B LC_CTYPE
category of the
current locale.
.PP
The function
.BR wcsrtombs (3)
provides a better interface to the same functionality.
.SH SEE ALSO
.BR mblen (3),
.BR mbstowcs (3),
.BR mbtowc (3),
.BR wcsrtombs (3)
.BR wctomb (3)