1MBSTOWCS(3) Linux Programmer's Manual MBSTOWCS(3)
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6 mbstowcs - convert a multibyte string to a wide-character string
7
9 #include <stdlib.h>
10 size_t mbstowcs(wchar_t *dest, const char *src, size_t n);
12
14 If dest is not NULL, the mbstowcs() function converts the multibyte
15 string src to a wide-character string starting at dest. At most n wide
16 characters are written to dest. The sequence of characters in the
17 string src shall begin in the initial shift state. The conversion can
18 stop for three reasons:
19 1. An invalid multibyte sequence has been encountered. In this case,
21 (size_t) -1 is returned.
22 2. n non-L'\0' wide characters have been stored at dest. In this case,
24 the number of wide characters written to dest is returned, but the
25 shift state at this point is lost.
26 3. The multibyte string has been completely converted, including the
28 terminating null character ('\0'). In this case, the number of wide
29 characters written to dest, excluding the terminating null wide
30 character, is returned.
31 The programmer must ensure that there is room for at least n wide char‐
33 acters at dest.
34 If dest is NULL, n is ignored, and the conversion proceeds as above,
36 except that the converted wide characters are not written out to mem‐
37 ory, and that no length limit exists.
38 In order to avoid the case 2 above, the programmer should make sure n
40 is greater than or equal to mbstowcs(NULL,src,0)+1.
41
43 The mbstowcs() function returns the number of wide characters that make
44 up the converted part of the wide-character string, not including the
45 terminating null wide character. If an invalid multibyte sequence was
46 encountered, (size_t) -1 is returned.
47
49 For an explanation of the terms used in this section, see
50 attributes(7).
51 ┌───────────┬───────────────┬─────────┐
53 │Interface │ Attribute │ Value │
54 ├───────────┼───────────────┼─────────┤
55 │mbstowcs() │ Thread safety │ MT-Safe │
56 └───────────┴───────────────┴─────────┘
58 POSIX.1-2001, POSIX.1-2008, C99.
59
61 The behavior of mbstowcs() depends on the LC_CTYPE category of the cur‐
62 rent locale.
63 The function mbsrtowcs(3) provides a better interface to the same func‐
65 tionality.
66
68 The program below illustrates the use of mbstowcs(), as well as some of
69 the wide character classification functions. An example run is the
70 following:
71 $ ./t_mbstowcs de_DE.UTF-8 Grüße!
73 Length of source string (excluding terminator):
74 8 bytes
75 6 multibyte characters
76 Wide character string is: Grüße! (6 characters)
78 G alpha upper
79 r alpha lower
80 ü alpha lower
81 ß alpha lower
82 e alpha lower
83 ! !alpha
84 Program source
86 #include <wctype.h>
88 #include <locale.h>
89 #include <wchar.h>
90 #include <stdio.h>
91 #include <string.h>
92 #include <stdlib.h>
93 int
95 main(int argc, char *argv[])
96 {
97 size_t mbslen; /* Number of multibyte characters in source */
98 wchar_t *wcs; /* Pointer to converted wide character string */
99 wchar_t *wp;
100 if (argc < 3) {
102 fprintf(stderr, "Usage: %s <locale> <string>\n", argv[0]);
103 exit(EXIT_FAILURE);
104 }
105 /* Apply the specified locale */
107 if (setlocale(LC_ALL, argv[1]) == NULL) {
109 perror("setlocale");
110 exit(EXIT_FAILURE);
111 }
112 /* Calculate the length required to hold argv[2] converted to
114 a wide character string */
115 mbslen = mbstowcs(NULL, argv[2], 0);
117 if (mbslen == (size_t) -1) {
118 perror("mbstowcs");
119 exit(EXIT_FAILURE);
120 }
121 /* Describe the source string to the user */
123 printf("Length of source string (excluding terminator):\n");
125 printf(" %zu bytes\n", strlen(argv[2]));
126 printf(" %zu multibyte characters\n\n", mbslen);
127 /* Allocate wide character string of the desired size. Add 1
129 to allow for terminating null wide character (L'\0'). */
130 wcs = calloc(mbslen + 1, sizeof(wchar_t));
132 if (wcs == NULL) {
133 perror("calloc");
134 exit(EXIT_FAILURE);
135 }
136 /* Convert the multibyte character string in argv[2] to a
138 wide character string */
139 if (mbstowcs(wcs, argv[2], mbslen + 1) == (size_t) -1) {
141 perror("mbstowcs");
142 exit(EXIT_FAILURE);
143 }
144 printf("Wide character string is: %ls (%zu characters)\n",
146 wcs, mbslen);
147 /* Now do some inspection of the classes of the characters in
149 the wide character string */
150 for (wp = wcs; *wp != 0; wp++) {
152 printf(" %lc ", (wint_t) *wp);
153 if (!iswalpha(*wp))
155 printf("!");
156 printf("alpha ");
157 if (iswalpha(*wp)) {
159 if (iswupper(*wp))
160 printf("upper ");
161 if (iswlower(*wp))
163 printf("lower ");
164 }
165 putchar('\n');
167 }
168 exit(EXIT_SUCCESS);
170 }
171
173 mblen(3), mbsrtowcs(3), mbtowc(3), wcstombs(3), wctomb(3)
174
176 This page is part of release 5.07 of the Linux man-pages project. A
177 description of the project, information about reporting bugs, and the
178 latest version of this page, can be found at
179 https://www.kernel.org/doc/man-pages/.
180GNU 2020-06-09 MBSTOWCS(3)