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Consistency: NULL pointer, but nul character.

.\" $NetBSD: wctomb.3,v 1.5 2006/10/14 07:51:01 wiz Exp $
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.Dd February 3, 2002
.Dt WCTOMB 3
.Os
.Sh NAME
.Nm wctomb
.Nd converts a wide character to a multibyte character
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In stdlib.h
.Ft int
.Fn wctomb "char * s" "const wchar_t wchar"
.Sh DESCRIPTION
The
.Fn wctomb
converts the wide character
.Fa wchar
to the corresponding multibyte character, and stores it in the array
pointed to by
.Fa s .
.Fn wctomb
may store at most
.Dv MB_CUR_MAX
bytes in the array.
.Pp
In state-dependent encoding,
.Fn wctomb
may store the special sequence to change the conversion state
before an actual multibyte character into the array pointed to by
.Fa s .
If
.Fa wchar
is a nul wide character
.Pq Sq \e0 ,
this function sets its own internal state to an initial conversion state.
.Pp
Calling any other functions in
.Lb libc
never changes the internal state of
.Fn wctomb ,
except changing the
.Dv LC_CTYPE
category of the current locale by calling
.Xr setlocale 3 .
Such
.Xr setlocale 3
calls cause the internal state of this function to be indeterminate.
.Pp
The behaviour of
.Fn wctomb
is affected by the
.Dv LC_CTYPE
category of the current locale.
.Pp
There is one special case:
.Bl -tag -width 012345678901
.It s == NULL
.Fn wctomb
initializes its own internal state to an initial state, and
determines whether the current encoding is state-dependent.
This function returns 0 if the encoding is state-independent,
otherwise non-zero.
In this case,
.Fa wchar
is completely ignored.
.El
.Sh RETURN VALUES
Normally,
.Fn wctomb
returns:
.Bl -tag -width 012345678901
.It positive
Number of bytes for the valid multibyte character pointed to by
.Fa s .
There are no cases that the value returned is greater than
.Fa n
or the value of the
.Dv MB_CUR_MAX
macro.
.It -1
.Fa wchar
is an invalid wide character.
.El
.Pp
If
.Fa s
is equal to
.Dv NULL ,
.Fn mbtowc
returns:
.Bl -tag -width 0123456789
.It 0
The current encoding is state-independent.
.It non-zero
The current encoding is state-dependent.
.El
.Sh ERRORS
No errors are defined.
.Sh SEE ALSO
.Xr setlocale 3
.Sh STANDARDS
The
.Fn wctomb
function conforms to
.St -ansiC .