Manpage of MBSTOWCS

MBSTOWCS

Section: Linux Programmer's Manual (3)
Updated: 2015-08-08
Index
 

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 destis not NULL, the mbstowcs() function converts the multibyte string srcto a wide-character string starting at dest. At most nwide 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) -1is returned.
2.
nnon-Laq\0aq wide characters have been stored at dest. In this case, the number of wide characters written to destis returned, but the shift state at this point is lost.
3.
The multibyte string has been completely converted, including the terminating null wide character (aq\0aq). 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 nwide characters at dest.

If destis NULL, nis 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 nis 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) -1is returned.  

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).
InterfaceAttributeValue
mbstowcs() Thread safetyMT-Safe
 

CONFORMING TO

POSIX.1-2001, POSIX.1-2008, C99.  

NOTES

The behavior of mbstowcs() depends on the LC_CTYPEcategory of the current locale.

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

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 (Laq\0aq). */

    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(aq\naq);
    }

    exit(EXIT_SUCCESS);
}
 

SEE ALSO

mblen(3), mbsrtowcs(3), mbtowc(3), wctomb(3), wcstombs(3)


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ATTRIBUTES
CONFORMING TO
NOTES
EXAMPLE
Program source
SEE ALSO

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Time: 22:27:54 GMT, June 20, 2016