wcslen, wcsnlen_s

 

C

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Technical Specifications

 

Strings library

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Null-terminated wide strings

Functions
Character manipulation
iswalnum (C95) iswalpha (C95) iswlower (C95) iswupper (C95) iswdigit (C95) iswxdigit (C95) iswblank (C99) wctype (C95) iswctype (C95)	iswcntrl (C95) iswgraph (C95) iswspace (C95) iswprint (C95) iswpunct (C95) towlower (C95) towupper (C95) wctrans (C95) towctrans (C95)
Conversions to numeric formats
wcstolwcstoll (C95)(C99) wcstoulwcstoull (C95)(C99)	wcstofwcstodwcstold (C99)(C95)(C99) wcstoimaxwcstoumax (C99)(C99)
String manipulation
wcslenwcsnlen_s (C95)(C11) wcscpywcscpy_s (C95)(C11) wcsncpywcsncpy_s (C95)(C11) wcscatwcscat_s (C95)(C11) wcsncatwcsncat_s (C95)(C11) wcsstr (C95)	wcscmp (C95) wcsncmp (C95) wcscoll (C95) wcsxfrm (C95) wcschr (C95) wcsrchr (C95) wcspbrk (C95) wcsspn (C95) wcscspn (C95) wcstokwcstok_s (C95)(C11)
Array manipulation
wmemcpywmemcpy_s (C95)(C11) wmemmovewmemmove_s (C95)(C11)	wmemcmp (C95) wmemchr (C95) wmemset (C95)

 

Defined in header <wchar.h>
size_t wcslen( const wchar_t *str );	(1)	(since C95)
size_t wcsnlen_s(const wchar_t *str, size_t strsz);	(2)	(since C11)

1) Returns the length of a wide string, that is the number of non-null wide characters that precede the terminating null wide character.

2) Same as (1), except that the function returns zero if str is a null pointer and returns strsz if the null wide character was not found in the first strsz wide characters of src

As with all bounds-checked functions, wcslen_s is only guaranteed to be available if __STDC_LIB_EXT1__ is defined by the implementation and if the user defines __STDC_WANT_LIB_EXT1__ to the integer constant 1 before including stdio.h..

Parameters

str	-	pointer to the null-terminated wide string to be examined
strsz	-	maximum number of wide characters to examine

Return value

1) The length of the null-terminated wide string str.

2) The length of the null-terminated wide string str on success, zero if str is a null pointer, strsz if the null wide character was not found.

Notes

strnlen_s and wcsnlen_s are the only bounds-checked functions that do not invoke the runtime constraints handler. They are pure utility functions used to provide limited support for non-null terminated strings.

Example

Run this code

#include <wchar.h>
#include <stdio.h>
 
int main(void)
{
    wchar_t str[] = L"How many wide characters does this string contain?";
 
    printf("without null character: %zu\n", wcslen(str));
    printf("with null character: %zu\n", sizeof str / sizeof *str);
}

Output:

without null character: 50
with null character: 51

References

• C11 standard (ISO/IEC 9899:2011):

• 7.29.4.6.1 The wcslen function (p: 439)

• K.3.9.2.4.1 The wcsnlen_s function (p: 646-647)

• C99 standard (ISO/IEC 9899:1999):

• 7.24.4.6.1 The wcslen function (p: 385)

See also

strlenstrnlen_s (C11)	returns the length of a given string (function)
C++ documentation for wcslen