# wcslen, wcsnlen_s

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< c‎ | string‎ | wide

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

strlen strnlen_s (C11) | returns the length of a given string (function)

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