std::wcsncmp

C++

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Technical Specifications

Strings library

Null-terminated strings

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Null-terminated wide strings

Functions
Character manipulation
iswalnum iswalpha iswlower iswupper iswdigit iswxdigit iswblank (C++11) wctype iswctype	iswcntrl iswgraph iswspace iswprint iswpunct towlower towupper wctrans towctrans
Conversions to numeric formats
wcstolwcstoll (C++11) wcstoulwcstoull (C++11)	wcstofwcstodwcstold (C++11)(C++11) wcstoimaxwcstouimax (C++11)(C++11)
String manipulation
wcslen wcscpy wcsncpy wcscat wcsncat wcscmp wcscoll wcsncmp	wcsxfrm wcschr wcsrchr wcspbrk wcsspn wcscspn wcsstr wcstok
Array manipulation
wmemcpy
wmemmove
wmemcmp
wmemchr
wmemset

Defined in header <cwchar>
int wcsncmp( const wchar_t* lhs, const wchar_t* rhs, std::size_t count );

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.

Example

Run this code

#include <iostream>
#include <cwchar>
#include <clocale>
#include <locale>

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

int main()
{
    const wchar_t str1[] = L"";
    const wchar_t str2[] = L" ";

    std::setlocale(LC_ALL, "en_US.utf8");
    std::wcout.imbue(std::locale("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 [ ]

See also

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