mbstowcs man page on Archlinux

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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 conversion starts in the initial
       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 wide 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.

CONFORMING TO
       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 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 <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), wctomb(3), wcstombs(3)

COLOPHON
       This  page  is  part of release 3.65 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

GNU				  2014-03-18			   MBSTOWCS(3)
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