man3/wcstombs.3

   1 .\" Copyright (c) Bruno Haible <haible@clisp.cons.org>
   2 .\"
   3 .\" SPDX-License-Identifier: GPL-2.0-or-later
   4 .\"
   5 .\" References consulted:
   6 .\"   GNU glibc-2 source code and manual
   7 .\"   Dinkumware C library reference http://www.dinkumware.com/
   8 .\"   OpenGroup's Single UNIX specification http://www.UNIX-systems.org/online.html
   9 .\"   ISO/IEC 9899:1999
  10 .\"
  11 .TH WCSTOMBS 3  2021-03-22 "GNU" "Linux Programmer's Manual"
  12 .SH NAME
  13 wcstombs \- convert a wide-character string to a multibyte string
  14 .SH LIBRARY
  15 Standard C library
  16 .RI ( libc ", " \-lc )
  17 .SH SYNOPSIS
  18 .nf
  19 .B #include <stdlib.h>
  20 .PP
  21 .BI "size_t wcstombs(char *restrict " dest ", const wchar_t *restrict " src ,
  22 .BI "                size_t " n );
  23 .fi
  24 .SH DESCRIPTION
  25 If
  26 .I dest
  27 is not NULL, the
  28 .BR wcstombs ()
  29 function converts
  30 the wide-character string
  31 .I src
  32 to a multibyte string starting at
  33 .IR dest .
  34 At most
  35 .I n
  36 bytes are written to
  37 .IR dest .
  38 The sequence of characters placed in
  39 .IR dest
  40 begins in the initial shift state.
  41 The conversion can stop for three reasons:
  42 .IP 1. 3
  43 A wide character has been encountered that can not be represented as a
  44 multibyte sequence (according to the current locale).
  45 In this case,
  46 .I (size_t)\ \-1
  47 is returned.
  48 .IP 2.
  49 The length limit forces a stop.
  50 In this case, the number of bytes written to
  51 .I dest
  52 is returned, but the shift state at this point is lost.
  53 .IP 3.
  54 The wide-character string has been completely converted, including the
  55 terminating null wide character (L\(aq\e0\(aq).
  56 In this case, the conversion ends in the initial shift state.
  57 The number of bytes written to
  58 .IR dest ,
  59 excluding the terminating null byte (\(aq\e0\(aq), is returned.
  60 .PP
  61 The programmer must ensure that there is room for at least
  62 .I n
  63 bytes
  64 at
  65 .IR dest .
  66 .PP
  67 If
  68 .IR dest
  69 is NULL,
  70 .I n
  71 is ignored, and the conversion proceeds as
  72 above, except that the converted bytes are not written out to memory,
  73 and no length limit exists.
  74 .PP
  75 In order to avoid the case 2 above, the programmer should make sure
  76 .I n
  77 is greater than or equal to
  78 .IR "wcstombs(NULL,src,0)+1" .
  79 .SH RETURN VALUE
  80 The
  81 .BR wcstombs ()
  82 function returns the number of bytes that make up the
  83 converted part of a multibyte sequence,
  84 not including the terminating null byte.
  85 If a wide character was encountered which could not be
  86 converted,
  87 .I (size_t)\ \-1
  88 is returned.
  89 .SH ATTRIBUTES
  90 For an explanation of the terms used in this section, see
  91 .BR attributes (7).
  92 .ad l
  93 .nh
  94 .TS
  95 allbox;
  96 lbx lb lb
  97 l l l.
  98 Interface       Attribute       Value
  99 T{
 100 .BR wcstombs ()
 101 T}      Thread safety   MT-Safe
 102 .TE
 103 .hy
 104 .ad
 105 .sp 1
 106 .SH CONFORMING TO
 107 POSIX.1-2001, POSIX.1-2008, C99.
 108 .SH NOTES
 109 The behavior of
 110 .BR wcstombs ()
 111 depends on the
 112 .B LC_CTYPE
 113 category of the
 114 current locale.
 115 .PP
 116 The function
 117 .BR wcsrtombs (3)
 118 provides a better interface to the same functionality.
 119 .SH SEE ALSO
 120 .BR mblen (3),
 121 .BR mbstowcs (3),
 122 .BR mbtowc (3),
 123 .BR wcsrtombs (3),
 124 .BR wctomb (3)