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 characters 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 memory, 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 current locale.

       The function mbsrtowcs(3) provides a better interface to the same functionality.

EXAMPLES

       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 Grüße!
           Length of source string (excluding terminator):
               8 bytes
               6 multibyte characters

           Wide character string is: Grüße! (6 characters)
               G alpha upper
               r alpha lower
               ü alpha lower
               ß 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 */

           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(*wcs));
           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 (wchar_t *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

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       information  about  reporting  bugs,  and  the  latest  version  of  this   page,   can   be   found   at
       https://www.kernel.org/doc/man-pages/.

GNU                                                2020-11-01                                        MBSTOWCS(3)