# wmemcmp

From cppreference.com
< c‎ | string‎ | wide

Defined in header ``<wchar.h>`` |  |
int wmemcmp( const wchar_t* lhs, const wchar_t* rhs, size_t count ); |  | (since C95)

Compares the first count wide characters of the wide character (or compatible integer type) arrays pointed to by lhs and rhs. The comparison is done lexicographically.

The sign of the result is the sign of the difference between the values of the first pair of wide characters that differ in the arrays being compared.

If `count` is zero, the function does nothing.

### Parameters

lhs, rhs | - | pointers to the wide character arrays to compare
count | - | number of wide characters to examine

### Return value

Negative value if the value of the first differing wide character in lhs is less than the value of the corresponding wide character in rhs: lhs precedes rhs in lexicographical order.

​0​ if all count wide characters of lhs and rhs are equal.

Positive value if the value of the first differing wide character in lhs is greater than the value of the corresponding wide character in rhs: rhs precedes lhs in lexicographical order.

### Notes

This function is not locale-sensitive and pays no attention to the values of the wchar_t objects it examines: nulls as well as invalid wide characters are compared too.

### Example

Run this code

    #include <locale.h>
    #include <stdio.h>
    #include <wchar.h>

    void demo(const wchar_t* lhs, const wchar_t* rhs, size_t sz)
    {
        for (size_t n = 0; n < sz; ++n)
            putwchar(lhs[n]);

        int rc = wmemcmp(lhs, rhs, sz);
        if (rc == 0)
            wprintf(L" compares equal to ");
        else if(rc < 0)
            wprintf(L" precedes ");
        else if(rc > 0)
            wprintf(L" follows ");

        for (size_t n = 0; n < sz; ++n)
            putwchar(rhs[n]);
        wprintf(L" in lexicographical order\n");
    }

    int main(void)
    {
        setlocale(LC_ALL, "en_US.utf8");

        wchar_t a1[] = {L'α',L'β',L'γ'};
        wchar_t a2[] = {L'α',L'β',L'δ'};

        size_t sz = sizeof a1 / sizeof *a1;
        demo(a1, a2, sz);
        demo(a2, a1, sz);
        demo(a1, a1, sz);
    }

Output:

    αβγ precedes αβδ in lexicographical order
    αβδ follows αβγ in lexicographical order
    αβγ compares equal to αβγ in lexicographical order

### References

- C23 standard (ISO/IEC 9899:2024):

  - 7.29.4.4.5 The wmemcmp function (p: TBD)

- C17 standard (ISO/IEC 9899:2018):

  - 7.29.4.4.5 The wmemcmp function (p: TBD)

- C11 standard (ISO/IEC 9899:2011):

  - 7.29.4.4.5 The wmemcmp function (p: 435)

- C99 standard (ISO/IEC 9899:1999):

  - 7.24.4.4.5 The wmemcmp function (p: 381)

### See also

wcscmp (C95) | compares two wide strings (function)
memcmp | compares two buffers (function)
wcsncmp (C95) | compares a certain amount of characters from two wide strings (function)
C++ documentation for wmemcmp

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