#include <stdlib.h>
size_t mbstowcs(wchar_t *restrict dest, const char *restrict src,
size_t n);
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.
| Interface | Attribute | Value |
| mbstowcs() | Thread safety | MT-Safe |
The function mbsrtowcs(3) provides a better interface to the same functionality.
$ ./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
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');
}