wcsncmp

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

Compares at most count wide characters of two null-terminated wide strings. 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 strings being compared.

The behavior is undefined if lhs or rhs are not pointers to null-terminated strings.

Parameters

lhs, rhs	-	pointers to the null-terminated wide strings to compare
count	-	maximum number of characters to compare

Return value

Negative value if lhs appears before rhs in lexicographical order.

Zero if lhs and rhs compare equal.

Positive value if lhs appears after rhs in lexicographical order.

Notes

This function is not locale-sensitive, unlike wcscoll and wcsxfrm.

Example

Run this code

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

void demo(const wchar_t *lhs, const wchar_t *rhs, int sz)
{
    int rc = wcsncmp(lhs, rhs, sz);
    if(rc == 0)
        printf("First%d characters of [%ls] equal [%ls]\n", sz, lhs, rhs);
    else if(rc < 0)
        printf("First%d characters of [%ls] precede [%ls]\n", sz, lhs, rhs);
    else if(rc > 0)
        printf("First%d characters of [%ls] follow [%ls]\n", sz, lhs, rhs);
}

int main(void)
{
    const wchar_t *str1 = L"";
    const wchar_t *str2 = L" ";

    setlocale(LC_ALL, "en_US.utf8");
    demo(str1, str2, 5);
    demo(str2, str1, 8);
    demo(str1, str2, 2);
}

Output:

First 5 characters of [] precede [ ]
First 8 characters of [ ] follow []
First 2 characters of [] equal [ ]

References

C11 standard (ISO/IEC 9899:2011):

7.29.4.4.3 The wcsncmp function (p: 434)

C99 standard (ISO/IEC 9899:1999):

7.24.4.4.3 The wcsncmp function (p: 380)

Language
Headers
Type support
Program utilities
Variadic function support
Error handling
Dynamic memory management
Date and time utilities
Strings library
Algorithms
Numerics
Input/output support
Localization support
Atomic operations (C11)
Thread support (C11)
Technical Specifications

wcscmp (C95)	compares two wide strings (function)
wmemcmp (C95)	compares a certain amount of wide characters from two arrays (function)
wcscoll (C95)	compares two wide strings in accordance to the current locale (function)