.\" $OpenBSD: wcstombs.3,v 1.4 2010/09/10 18:38:19 jmc Exp $
.\" $NetBSD: wcstombs.3,v 1.5 2003/09/08 17:54:32 wiz Exp $
.\"
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.Dd $Mdocdate: September 10 2010 $
.Dt WCSTOMBS 3
.Os
.\" ----------------------------------------------------------------------
.Sh NAME
.Nm wcstombs
.Nd converts a wide-character string to a multibyte character string
.\" ----------------------------------------------------------------------
.Sh SYNOPSIS
.Fd #include <stdlib.h>
.Ft size_t
.Fn wcstombs "char * restrict s" "const wchar_t * restrict pwcs" "size_t n"
.\" ----------------------------------------------------------------------
.Sh DESCRIPTION
.Fn wcstombs
converts the null-terminated wide-character string pointed to by
.Fa pwcs
to the corresponding multibyte character string,
and stores it in the array pointed to by
.Fa s .
This function may modify the first at most
.Fa n
bytes of the array pointed to by
.Fa s .
Each character will be converted as if
.Xr wctomb 3
is continuously called, except the internal state of
.Xr wctomb 3
will not be affected.
.Pp
For state-dependent encoding, the
.Fn wcstombs
implies the result multibyte character string pointed to by
.Fa s
always to begin with an initial state.
.Pp
The behaviour of the
.Fn wcstombs
is affected by the
.Dv LC_CTYPE
category of the current locale.
.Pp
There are special cases:
.Bl -tag -width 012345678901
.It s == NULL
The
.Fn wcstombs
returns the number of bytes to store the whole multibyte character string
corresponding to the wide-character string pointed to by
.Fa pwcs .
In this case,
.Fa n
is ignored.
.It pwcs == NULL
Undefined (may causes the program to crash).
.El
.\" ----------------------------------------------------------------------
.Sh RETURN VALUES
.Fn wcstombs
returns:
.Bl -tag -width 012345678901
.It 0 or positive
Number of bytes stored in the array pointed to by
.Fa s .
There are no cases that the value returned is greater than
.Fa n
(unless
.Fa s
is a null pointer).
If the return value is equal to
.Fa n ,
the string pointed to by
.Fa s
will not be null-terminated.
.It (size_t)-1
.Fa pwcs
points the string containing invalid wide character.
.Fn wcstombs
also sets
.Va errno
to indicate the error.
.El
.\" ----------------------------------------------------------------------
.Sh ERRORS
.Fn wcstombs
may cause an error in the following cases:
.Bl -tag -width Er
.It Bq Er EILSEQ
.Fa pwcs
Points to the string containing invalid wide character.
.El
.\" ----------------------------------------------------------------------
.Sh SEE ALSO
.Xr setlocale 3 ,
.Xr wctomb 3
.\" ----------------------------------------------------------------------
.Sh STANDARDS
The
.Fn wcstombs
function conforms to
.St -ansiC .
The restrict qualifier is added at
.\" .St -isoC99 .
ISO/IEC 9899/1999
.Pq Dq ISO C99 .