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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ATTRIBUTES | CONFORMING TO | NOTES | EXAMPLE | SEE ALSO | COLOPHON |
MBSTOWCS(3) Linux Programmer's Manual MBSTOWCS(3)
mbstowcs - convert a multibyte string to a wide-character string
#include <stdlib.h>
size_t mbstowcs(wchar_t *dest, const char *src, size_t n);
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.
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.
For an explanation of the terms used in this section, see
attributes(7).
┌───────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├───────────┼───────────────┼─────────┤
│mbstowcs() │ Thread safety │ MT-Safe │
└───────────┴───────────────┴─────────┘
POSIX.1-2001, POSIX.1-2008, C99.
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.
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 */
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);
}
mblen(3), mbsrtowcs(3), mbtowc(3), wcstombs(3), wctomb(3)
This page is part of release 4.12 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 2016-10-08 MBSTOWCS(3)
Pages that refer to this page: MB_CUR_MAX(3), mbsrtowcs(3), mbtowc(3), wcstombs(3), wctomb(3), wprintf(3), locale(7)