man3/mbstowcs.3

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  12 .\" References consulted:
  13 .\"   GNU glibc-2 source code and manual
  14 .\"   Dinkumware C library reference http://www.dinkumware.com/
  15 .\"   OpenGroup's Single UNIX specification http://www.UNIX-systems.org/online.html
  16 .\"   ISO/IEC 9899:1999
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  18 .TH MBSTOWCS 3  2016-10-08 "GNU" "Linux Programmer's Manual"
  19 .SH NAME
  20 mbstowcs \- convert a multibyte string to a wide-character string
  21 .SH SYNOPSIS
  22 .nf
  23 .B #include <stdlib.h>
  24 .sp
  25 .BI "size_t mbstowcs(wchar_t *" dest ", const char *" src ", size_t " n );
  26 .fi
  27 .SH DESCRIPTION
  28 If
  29 .I dest
  30 is not NULL,
  31 the
  32 .BR mbstowcs ()
  33 function converts the
  34 multibyte string
  35 .I src
  36 to a wide-character string starting at
  37 .IR dest .
  38 At most
  39 .I n
  40 wide characters are written to
  41 .IR dest .
  42 The sequence of characters in the string
  43 .I src
  44 shall begin in the initial shift state.
  45 The conversion can stop for three reasons:
  46 .IP 1. 3
  47 An invalid multibyte sequence has been encountered.
  48 In this case,
  49 .I (size_t)\ \-1
  50 is returned.
  51 .IP 2.
  52 .I n
  53 non-L\(aq\\0\(aq wide characters have been stored at
  54 .IR dest .
  55 In this case, the number of wide characters written to
  56 .I dest
  57 is returned, but the
  58 shift state at this point is lost.
  59 .IP 3.
  60 The multibyte string has been completely converted, including the
  61 terminating null character (\(aq\\0\(aq).
  62 In this case, the number of wide characters written to
  63 .IR dest ,
  64 excluding the terminating null wide character, is returned.
  65 .PP
  66 The programmer must ensure that there is room for at least
  67 .I n
  68 wide
  69 characters at
  70 .IR dest .
  71 .PP
  72 If
  73 .IR dest
  74 is NULL,
  75 .I n
  76 is ignored, and the conversion proceeds as
  77 above, except that the converted wide characters are not written out to memory,
  78 and that no length limit exists.
  79 .PP
  80 In order to avoid the case 2 above, the programmer should make sure
  81 .I n
  82 is
  83 greater than or equal to
  84 .IR "mbstowcs(NULL,src,0)+1" .
  85 .SH RETURN VALUE
  86 The
  87 .BR mbstowcs ()
  88 function returns the number of wide characters that make
  89 up the converted part of the wide-character string, not including the
  90 terminating null wide character.
  91 If an invalid multibyte sequence was
  92 encountered,
  93 .I (size_t)\ \-1
  94 is returned.
  95 .SH ATTRIBUTES
  96 For an explanation of the terms used in this section, see
  97 .BR attributes (7).
  98 .TS
  99 allbox;
 100 lb lb lb
 101 l l l.
 102 Interface       Attribute       Value
 103 T{
 104 .BR mbstowcs ()
 105 T}      Thread safety   MT-Safe
 106 .TE
 107 .SH CONFORMING TO
 108 POSIX.1-2001, POSIX.1-2008, C99.
 109 .SH NOTES
 110 The behavior of
 111 .BR mbstowcs ()
 112 depends on the
 113 .B LC_CTYPE
 114 category of the
 115 current locale.
 116 .PP
 117 The function
 118 .BR mbsrtowcs (3)
 119 provides a better interface to the same
 120 functionality.
 121 .SH EXAMPLE
 122 The program below illustrates the use of
 123 .BR mbstowcs (),
 124 as well as some of the wide character classification functions.
 125 An example run is the following:
 126 .in +4n
 127 .nf
 128
 129 $ ./t_mbstowcs de_DE.UTF\-8 Grüße!
 130 Length of source string (excluding terminator):
 131     8 bytes
 132     6 multibyte characters
 133
 134 Wide character string is: Grüße! (6 characters)
 135     G alpha upper
 136     r alpha lower
 137     ü alpha lower
 138     ß alpha lower
 139     e alpha lower
 140     ! !alpha
 141 .fi
 142 .in
 143 .SS Program source
 144 .nf
 145 #include <wctype.h>
 146 #include <locale.h>
 147 #include <wchar.h>
 148 #include <stdio.h>
 149 #include <string.h>
 150 #include <stdlib.h>
 151
 152 int
 153 main(int argc, char *argv[])
 154 {
 155     size_t mbslen;      /* Number of multibyte characters in source */
 156     wchar_t *wcs;       /* Pointer to converted wide character string */
 157     wchar_t *wp;
 158
 159     if (argc < 3) {
 160         fprintf(stderr, "Usage: %s <locale> <string>\\n", argv[0]);
 161         exit(EXIT_FAILURE);
 162     }
 163
 164     /* Apply the specified locale */
 165
 166     if (setlocale(LC_ALL, argv[1]) == NULL) {
 167         perror("setlocale");
 168         exit(EXIT_FAILURE);
 169     }
 170
 171     /* Calculate the length required to hold argv[2] converted to
 172        a wide character string */
 173
 174     mbslen = mbstowcs(NULL, argv[2], 0);
 175     if (mbslen == (size_t) \-1) {
 176         perror("mbstowcs");
 177         exit(EXIT_FAILURE);
 178     }
 179
 180     /* Describe the source string to the user */
 181
 182     printf("Length of source string (excluding terminator):\\n");
 183     printf("    %zu bytes\\n", strlen(argv[2]));
 184     printf("    %zu multibyte characters\\n\\n", mbslen);
 185
 186     /* Allocate wide character string of the desired size.  Add 1
 187        to allow for terminating null wide character (L\(aq\\0\(aq). */
 188
 189     wcs = calloc(mbslen + 1, sizeof(wchar_t));
 190     if (wcs == NULL) {
 191         perror("calloc");
 192         exit(EXIT_FAILURE);
 193     }
 194
 195     /* Convert the multibyte character string in argv[2] to a
 196        wide character string */
 197
 198     if (mbstowcs(wcs, argv[2], mbslen + 1) == (size_t) \-1) {
 199         perror("mbstowcs");
 200         exit(EXIT_FAILURE);
 201     }
 202
 203     printf("Wide character string is: %ls (%zu characters)\\n",
 204             wcs, mbslen);
 205
 206     /* Now do some inspection of the classes of the characters in
 207        the wide character string */
 208
 209     for (wp = wcs; *wp != 0; wp++) {
 210         printf("    %lc ", (wint_t) *wp);
 211
 212         if (!iswalpha(*wp))
 213             printf("!");
 214         printf("alpha ");
 215
 216         if (iswalpha(*wp)) {
 217             if (iswupper(*wp))
 218                 printf("upper ");
 219
 220             if (iswlower(*wp))
 221                 printf("lower ");
 222         }
 223
 224         putchar(\(aq\\n\(aq);
 225     }
 226
 227     exit(EXIT_SUCCESS);
 228 }
 229 .fi
 230 .SH SEE ALSO
 231 .BR mblen (3),
 232 .BR mbsrtowcs (3),
 233 .BR mbtowc (3),
 234 .BR wcstombs (3),
 235 .BR wctomb (3)