# mbstowcs

## NAME



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


## LIBRARY



           Standard C library (_libc_ , _-lc_)
    


## SYNOPSIS



           **#include <stdlib.h>**
    
           **size_t mbstowcs(** size_t dsize;
                           **wchar_t** _dest_**[restrict** _dsize_**], const char *restrict** _src_**,**
                           **size_t** _dsize_**);**
    


## DESCRIPTION



           If _dest_ is not NULL, convert the multibyte string _src_ to a wide-
           character string starting at _dest_.  At most _dsize_ 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:
    
           •  An invalid multibyte sequence has been encountered.  In this
              case, _(size_t) -1_ is returned.
    
           •  _dsize_ 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.
    
           •  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.
    
           If _dest_ is NULL, _dsize_ 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 _dsize_ is greater than or equal to _mbstowcs(NULL,src,0)+1_.
    
           The programmer must ensure that there is room for at least _dsize_
           wide characters at _dest_.
    


## RETURN VALUE



           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 │
           └──────────────────────────────────────┴───────────────┴─────────┘
    


## VERSIONS



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


## STANDARDS



           C11, POSIX.1-2008.
    


## NOTES



           The behavior of **mbstowcs**() depends on the **LC_CTYPE** category of the
           current locale.
    


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


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