mbstowcs(3)



MBSTOWCS(3)                Linux Programmer's Manual               MBSTOWCS(3)

NAME
       mbstowcs - convert a multibyte string to a wide-character string

SYNOPSIS
       #include <stdlib.h>

       size_t mbstowcs(wchar_t *dest, const char *src, size_t n);

DESCRIPTION
       If  dest  is  not  NULL, the mbstowcs() function converts the multibyte
       string src to a wide-character string starting at dest.  At most n wide
       characters  are  written  to  dest.   The sequence of characters in the
       string src shall begin in the initial shift state.  The conversion  can
       stop for three reasons:

       1. An  invalid  multibyte sequence has been encountered.  In this case,
          (size_t) -1 is returned.

       2. n non-L'\0' wide characters have been stored at dest.  In this case,
          the  number  of wide characters written to dest is returned, but the
          shift state at this point is lost.

       3. The multibyte string has been completely  converted,  including  the
          terminating null character ('\0').  In this case, the number of wide
          characters written to dest,  excluding  the  terminating  null  wide
          character, is returned.

       The programmer must ensure that there is room for at least n wide char-
       acters at dest.

       If dest is NULL, n is ignored, and the conversion  proceeds  as  above,
       except  that  the converted wide characters are not written out to mem-
       ory, and that no length limit exists.

       In order to avoid the case 2 above, the programmer should make  sure  n
       is greater than or equal to mbstowcs(NULL,src,0)+1.

RETURN VALUE
       The mbstowcs() function returns the number of wide characters that make
       up the converted part of the wide-character string, not  including  the
       terminating  null wide character.  If an invalid multibyte sequence was
       encountered, (size_t) -1 is returned.

ATTRIBUTES
       For  an  explanation  of  the  terms  used   in   this   section,   see
       attributes(7).

       +-----------+---------------+---------+
       |Interface  | Attribute     | Value   |
       +-----------+---------------+---------+
       |mbstowcs() | Thread safety | MT-Safe |
       +-----------+---------------+---------+
CONFORMING TO
       POSIX.1-2001, POSIX.1-2008, C99.

NOTES
       The behavior of mbstowcs() depends on the LC_CTYPE category of the cur-
       rent locale.

       The function mbsrtowcs(3) provides a better interface to the same func-
       tionality.

EXAMPLE
       The program below illustrates the use of mbstowcs(), as well as some of
       the wide character classification functions.  An  example  run  is  the
       following:

           $ ./t_mbstowcs de_DE.UTF-8 GruBe!
           Length of source string (excluding terminator):
               8 bytes
               6 multibyte characters

           Wide character string is: GruBe! (6 characters)
               G alpha upper
               r alpha lower
               u alpha lower
               B alpha lower
               e alpha lower
               ! !alpha

   Program source

       #include <wctype.h>
       #include <locale.h>
       #include <wchar.h>
       #include <stdio.h>
       #include <string.h>
       #include <stdlib.h>

       int
       main(int argc, char *argv[])
       {
           size_t mbslen;      /* Number of multibyte characters in source */
           wchar_t *wcs;       /* Pointer to converted wide character string */
           wchar_t *wp;

           if (argc < 3) {
               fprintf(stderr, "Usage: %s <locale> <string>\n", argv[0]);
               exit(EXIT_FAILURE);
           }

           /* Apply the specified locale */

           if (setlocale(LC_ALL, argv[1]) == NULL) {
               perror("setlocale");
               exit(EXIT_FAILURE);
           }

           /* Calculate the length required to hold argv[2] converted to
              a wide character string */

           mbslen = mbstowcs(NULL, argv[2], 0);
           if (mbslen == (size_t) -1) {
               perror("mbstowcs");
               exit(EXIT_FAILURE);
           }

           /* Describe the source string to the user */

           printf("Length of source string (excluding terminator):\n");
           printf("    %zu bytes\n", strlen(argv[2]));
           printf("    %zu multibyte characters\n\n", mbslen);

           /* Allocate wide character string of the desired size.  Add 1
              to allow for terminating null wide character (L'\0'). */

           wcs = calloc(mbslen + 1, sizeof(wchar_t));
           if (wcs == NULL) {
               perror("calloc");
               exit(EXIT_FAILURE);
           }

           /* Convert the multibyte character string in argv[2] to a
              wide character string */

           if (mbstowcs(wcs, argv[2], mbslen + 1) == (size_t) -1) {
               perror("mbstowcs");
               exit(EXIT_FAILURE);
           }

           printf("Wide character string is: %ls (%zu characters)\n",
                   wcs, mbslen);

           /* Now do some inspection of the classes of the characters in
              the wide character string */

           for (wp = wcs; *wp != 0; wp++) {
               printf("    %lc ", (wint_t) *wp);

               if (!iswalpha(*wp))
                   printf("!");
               printf("alpha ");

               if (iswalpha(*wp)) {
                   if (iswupper(*wp))
                       printf("upper ");

                   if (iswlower(*wp))
                       printf("lower ");
               }

               putchar('\n');
           }

           exit(EXIT_SUCCESS);
       }

SEE ALSO
       mblen(3), mbsrtowcs(3), mbtowc(3), wcstombs(3), wctomb(3)

COLOPHON
       This  page  is  part of release 4.16 of the Linux man-pages project.  A
       description of the project, information about reporting bugs,  and  the
       latest     version     of     this    page,    can    be    found    at
       https://www.kernel.org/doc/man-pages/.

GNU                               2017-09-15                       MBSTOWCS(3)

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